GUARANTEE

Exhibit 10.4

Execution Version

GUARANTEE dated as of July 30, 2004, made among ROCKWOOD SPECIALTIES INTERNATIONAL, INC., a Delaware corporation ("Holdings"), each of the subsidiaries of ROCKWOOD SPECIALTIES GROUP, INC., a Delaware corporation (the "US Borrower"), listed on Annex A hereto (each such subsidiary individually, a "Subsidiary Guarantor" and, collectively, the "Subsidiary Guarantors"; the Subsidiary Guarantors and Holdings are referred to collectively as the "Guarantors") and CREDIT SUISSE FIRST BOSTON, acting through its Cayman Islands Branch, as administrative agent (in such capacity, the "Administrative Agent") for the lenders (the "Lenders") from time to time parties to the Credit Agreement dated as of July 30, 2004 (as the same may be amended, supplemented or otherwise modified from time to time, the "Credit Agreement"), among the US Borrower, Rockwood Specialties Limited, a company incorporated under the laws of England and Wales (the "UK Borrower" and, together with the US Borrower, the "Borrowers"), Holdings, the Lenders, the Administrative Agent and UBS Securities LLC and Xxxxxxx Xxxxx Credit Partners L.P., as co-syndication agents (in such capacities, the "Co-Syndication Agents") for the Lenders.

W I T N E S S E T H:

WHEREAS, (a) pursuant to the Credit Agreement, the Lenders have severally agreed to make Loans to the Borrowers and the Letter of Credit Issuer has agreed to issue Letters of Credit for the account of the Borrowers (collectively, the "Extensions of Credit") upon the terms and subject to the conditions set forth therein and (b) one or more Lenders or Affiliates of Lenders may from time to time enter into Hedge Agreements with the Borrowers or any of the Restricted Subsidiaries;

WHEREAS, each Subsidiary Guarantor is a Domestic Subsidiary of the US Borrower;

WHEREAS, the proceeds of the Extensions of Credit will be used in part to enable the Borrowers to make valuable transfers to the Subsidiary Guarantors in connection with the operation of their respective businesses;

WHEREAS, each Guarantor acknowledges that it will derive substantial direct and indirect benefit from the making of the Extensions of Credit; and

WHEREAS, it is a condition precedent to the obligation of the Lenders and the Letter of Credit Issuer to make their respective Extensions of Credit to the Borrowers under the Credit Agreement that the Guarantors shall have executed and delivered this Guarantee to the Administrative Agent for the ratable benefit of the Secured Parties;

NOW, THEREFORE, in consideration of the premises and to induce the Administrative Agent, the Co-Syndication Agents, the Lenders and the Letter of Credit Issuer to enter into the Credit Agreement and to induce the Lenders and the Letter of Credit Issuer to make their respective Extensions of Credit to the Borrowers under the Credit Agreement and to induce one or more Lenders or Affiliates of Lenders to enter into Hedge Agreements with the Borrowers and/or the Restricted Subsidiaries, the Guarantors hereby agree with the Administrative Agent, for the ratable benefit of the Secured Parties, as follows:

1. Defined Terms.

(a) Unless otherwise defined herein, terms defined in the Credit Agreement and used herein shall have the meanings given to them in the Credit Agreement.

(b) As used herein, the term "Closing Time" means 24:00 (German time) on the Closing Date.

(c) As used herein, the term "Obligations" means the collective reference to (i) the due and punctual payment of (x) the principal of and premium, if any, and interest at the applicable rate provided in the Credit Agreement (including interest accruing during the pendency of any bankruptcy, insolvency, receivership or other similar proceeding, regardless of whether allowed or allowable in such proceeding) on the Loans, when and as due, whether at maturity, by acceleration, upon one or more dates set for prepayment or otherwise, (y) each payment required to be made by the Borrowers under the Credit Agreement in respect of any Letter of Credit, when and as due, including payments in respect of reimbursement of disbursements, interest thereon and obligations to provide cash collateral, and (z) all other monetary obligations, including fees, costs, expenses and indemnities, whether primary, secondary, direct, contingent, fixed or otherwise (including monetary obligations incurred during the pendency of any bankruptcy, insolvency, receivership or other similar proceeding, regardless of whether allowed or allowable in such proceeding), of the Borrowers or any other Credit Party to any of the Secured Parties under the Credit Agreement and the other Credit Documents, (ii) the due and punctual performance of all covenants, agreements, obligations and liabilities of the Borrowers under or pursuant to the Credit Agreement and the other Credit Documents, (iii) the due and punctual payment and performance of all the covenants, agreements, obligations and liabilities of each other Credit Party under or pursuant to this Guarantee or the other Credit Documents, (iv) the due and punctual payment and performance of all obligations of each Borrower or Restricted Subsidiary under each Hedge Agreement that (x) is in effect on the Closing Date with a counterparty that is a Lender or an Affiliate of a Lender as of the Closing Date or (y) is entered into after the Closing Date with any counterparty that is a Lender or an Affiliate of a Lender at the time such Hedge Agreement is entered into and (v) the due and punctual payment and performance of all obligations in respect of overdrafts and related liabilities owed to the Administrative Agent or its Affiliates arising from or in connection with treasury, depositary or cash management services or in connection with any automated clearinghouse transfer of funds.

(d) As used herein, the term "Secured Parties" means (i) the Lenders, (ii) the Letter of Credit Issuer, (iii) the Swingline Lender, (iv) the Administrative Agent, (v) the Co-Syndication Agents, (vi) each counterparty to a Hedge Agreement the obligations under which constitute Obligations, (viii) the beneficiaries of each indemnification obligation undertaken by any Credit Party under any Credit Document and (ix) any successors, indorsees, transferees and assigns of each of the foregoing.

(e) References to "Lenders" in this Guarantee shall be deemed to include Affiliates of Lenders that may from time to time enter into Hedge Agreements with any Borrower or Restricted Subsidiary.

(f) The words "hereof," "herein" and "hereunder" and words of similar import when used in this Guarantee shall refer to this Guarantee as a whole and not to any particular provision of this Guarantee, and Section references are to Sections of this Guarantee unless otherwise specified. The words "include", "includes" and "including" shall be deemed to be followed by the phrase "without limitation".

(g) The meanings given to terms defined herein shall be equally applicable to both the singular and plural forms of such terms.

2. Guarantee.

(a) Subject to the provisions of Section 2(b) and effective immediately upon the Closing Time, each of the Guarantors hereby, jointly and severally, unconditionally and irrevocably, guarantees, as primary obligor and not merely as surety, to the Administrative Agent, for the ratable benefit of the Secured Parties, the prompt and complete payment and performance when due (whether at the stated maturity, by acceleration or otherwise) of the Obligations.

(b) Anything herein or in any other Credit Document to the contrary notwithstanding, the maximum liability of each Guarantor hereunder and under the other Credit Documents shall in no

event exceed the amount that can be guaranteed by such Guarantor under applicable laws relating to the insolvency of debtors.

(c) Each Guarantor further agrees to pay any and all expenses (including all fees and disbursements of counsel) that may be paid or incurred by the Administrative Agent or any other Secured Party in enforcing, or obtaining advice of counsel in respect of, any rights with respect to, or collecting, any or all of the Obligations and/or enforcing any rights with respect to, or collecting against, such Guarantor under this Guarantee.

(d) Each Guarantor agrees that the Obligations may at any time and from time to time exceed the amount of the liability of such Guarantor hereunder without impairing this Guarantee or affecting the rights and remedies of the Administrative Agent or any other Secured Party hereunder.

(e) No payment or payments made by the Borrowers, any of the Guarantors, any other guarantor or any other Person or received or collected by the Administrative Agent or any other Secured Party from the Borrowers, any of the Guarantors, any other guarantor or any other Person by virtue of any action or proceeding or any set-off or appropriation or application at any time or from time to time in reduction of or in payment of the Obligations shall be deemed to modify, reduce, release or otherwise affect the liability of any Guarantor hereunder, which shall, notwithstanding any such payment or payments other than payments made by such Guarantor in respect of the Obligations or payments received or collected from such Guarantor in respect of the Obligations, remain liable for the Obligations up to the maximum liability of such Guarantor hereunder until the Obligations under the Credit Documents are paid in full, the Commitments are terminated and no Letters of Credit shall be outstanding.

(f) Each Guarantor agrees that whenever, at any time, or from time to time, it shall make any payment to the Administrative Agent or any other Secured Party on account of its liability hereunder, it will notify the Administrative Agent in writing that such payment is made under this Guarantee for such purpose.

3. Right of Contribution. Each Guarantor hereby agrees that to the extent that a Guarantor shall have paid more than its proportionate share of any payment made hereunder, such Guarantor shall be entitled to seek and receive contribution from and against any other Guarantor hereunder who has not paid its proportionate share of such payment. Each Guarantor's right of contribution shall be subject to the terms and conditions of Section 5 hereof. The provisions of this Section 3 shall in no respect limit the obligations and liabilities of any Guarantor to the Administrative Agent and the other Secured Parties, and each Guarantor shall remain liable to the Administrative Agent and the other Secured Parties for the full amount guaranteed by such Guarantor hereunder.

4. Right of Set-off. In addition to any rights and remedies of the Secured Parties provided by law, each Guarantor hereby irrevocably authorizes each Secured Party at any time and from time to time following the occurrence and during the continuance of an Event of Default without notice to such Guarantor or any other Guarantor, any such notice being expressly waived by each Guarantor, upon any amount becoming due and payable by such Guarantor hereunder (whether at stated maturity, by acceleration or otherwise) to set-off and appropriate and apply against such amount any and all deposits (general or special, time or demand, provisional or final), in any currency, and any other credits, indebtedness or claims, in any currency, in each case whether direct or indirect, absolute or contingent, matured or unmatured, at any time held or owing by such Secured Party to or for the credit or the account of such Guarantor. Each Secured Party shall notify such Guarantor promptly of any such set-off and the appropriation and application made by such Secured Party, provided that the failure to give such notice shall not affect the validity of such set-off and application.

5. No Subrogation. Notwithstanding any payment or payments made by any of the Guarantors hereunder or any set-off or appropriation and application of funds of any of the Guarantors by the

Administrative Agent or any other Secured Party, no Guarantor shall be entitled to be subrogated to any of the rights of the Administrative Agent or any other Secured Party against the Borrowers or any other Guarantor or any collateral security or guarantee or right of offset held by the Administrative Agent or any other Secured Party for the payment of the Obligations, nor shall any Guarantor seek or be entitled to seek any contribution or reimbursement from the Borrowers or any other Guarantor in respect of payments made by such Guarantor hereunder, until all amounts owing to the Administrative Agent and the other Secured Parties by the Credit Parties on account of the Obligations under the Credit Documents are paid in full, the Commitments are terminated and no Letters of Credit shall be outstanding. If any amount shall be paid to any Guarantor on account of such subrogation rights at any time when all the Obligations shall not have been paid in full, such amount shall be held by such Guarantor in trust for the Administrative Agent and the other Secured Parties, segregated from other funds of such Guarantor, and shall, forthwith upon receipt by such Guarantor, be turned over to the Administrative Agent in the exact form received by such Guarantor (duly indorsed by such Guarantor to the Administrative Agent, if required), to be applied against the Obligations, whether due or to become due, in such order as the Administrative Agent may determine.

6. Amendments, etc. with Respect to the Obligations; Waiver of Rights. Each Guarantor shall remain obligated hereunder notwithstanding that, without any reservation of rights against any Guarantor and without notice to or further assent by any Guarantor, (a) any demand for payment of any of the Obligations made by the Administrative Agent or any other Secured Party may be rescinded by such party and any of the Obligations continued, (b) the Obligations, or the liability of any other party upon or for any part thereof, or any collateral security or guarantee therefor or right of offset with respect thereto, may, from time to time, in whole or in part, be renewed, extended, amended, modified, accelerated, compromised, waived, surrendered or released by the Administrative Agent or any other Secured Party, (c) the Credit Agreement, the other Credit Documents, the Letters of Credit and any other documents executed and delivered in connection therewith and the Hedge Agreements and any other documents executed and delivered in connection therewith and any documents entered into with the Administrative Agent or any of its Affiliates in connection with treasury, depositary or cash management services or in connection with any automated clearinghouse transfer of funds may be amended, modified, supplemented or terminated, in whole or in part, as the Administrative Agent (or the Required Lenders, as the case may be, or, in the case of any Hedge Agreement or documents entered into with the Administrative Agent or any of its Affiliates in connection with treasury, depositary or cash management services or in connection with any automated clearinghouse transfer of funds, the party thereto) may deem advisable from time to time, and (d) any collateral security, guarantee or right of offset at any time held by the Administrative Agent or any other Secured Party for the payment of the Obligations may be sold, exchanged, waived, surrendered or released. Neither the Administrative Agent nor any other Secured Party shall have any obligation to protect, secure, perfect or insure any Lien at any time held by it as security for the Obligations or for this Guarantee or any property subject thereto. When making any demand hereunder against any Guarantor, the Administrative Agent or any other Secured Party may, but shall be under no obligation to, make a similar demand on the Borrowers or any Guarantor or guarantor, and any failure by the Administrative Agent or any other Secured Party to make any such demand or to collect any payments from the Borrowers or any Guarantor or guarantor or any release of the Borrowers or any Guarantor or guarantor shall not relieve any Guarantor in respect of which a demand or collection is not made or any Guarantor not so released of its several obligations or liabilities hereunder, and shall not impair or affect the rights and remedies, express or implied, or as a matter of law, of the Administrative Agent or any other Secured Party against any Guarantor. For the purposes hereof, "demand" shall include the commencement and continuance of any legal proceedings.

7. Guarantee Absolute and Unconditional. Each Guarantor waives any and all notice of the creation, contraction, incurrence, renewal, extension, amendment, waiver or accrual of any of the Obligations, and notice of or proof of reliance by the Administrative Agent or any other Secured Party

upon this Guarantee or acceptance of this Guarantee, the Obligations or any of them, shall conclusively be deemed to have been created, contracted or incurred, or renewed, extended, amended, waived or accrued, in reliance upon this Guarantee; and all dealings between the Borrowers and any of the Guarantors, on the one hand, and the Administrative Agent and the other Secured Parties, on the other hand, likewise shall be conclusively presumed to have been had or consummated in reliance upon this Guarantee. Each Guarantor waives diligence, presentment, protest, demand for payment and notice of default or nonpayment to or upon the Borrowers or any of the Guarantors with respect to the Obligations. Each Guarantor understands and agrees that this Guarantee shall be construed as a continuing, absolute and unconditional guarantee of payment without regard to (a) the validity, regularity or enforceability of the Credit Agreement, any other Credit Document, any Letter of Credit or any Hedge Agreement, any of the Obligations or any other collateral security therefor or guarantee or right of offset with respect thereto at any time or from time to time held by the Administrative Agent or any other Secured Party, (b) any defense, set-off or counterclaim (other than a defense of payment or performance) that may at any time be available to or be asserted by the Borrowers against the Administrative Agent or any other Secured Party or (c) any other circumstance whatsoever (with or without notice to or knowledge of the Borrowers or such Guarantor) that constitutes, or might be construed to constitute, an equitable or legal discharge of the Borrowers for the Obligations, or of such Guarantor under this Guarantee, in bankruptcy or in any other instance. When pursuing its rights and remedies hereunder against any Guarantor, the Administrative Agent and any other Secured Party may, but shall be under no obligation to, pursue such rights and remedies as it may have against the Borrowers or any other Person or against any collateral security or guarantee for the Obligations or any right of offset with respect thereto, and any failure by the Administrative Agent or any other Secured Party to pursue such other rights or remedies or to collect any payments from the Borrowers or any such other Person or to realize upon any such collateral security or guarantee or to exercise any such right of offset, or any release of the Borrowers or any such other Person or any such collateral security, guarantee or right of offset, shall not relieve such Guarantor of any liability hereunder, and shall not impair or affect the rights and remedies, whether express, implied or available as a matter of law, of the Administrative Agent and the other Secured Parties against such Guarantor. This Guarantee shall remain in full force and effect and be binding in accordance with and to the extent of its terms upon each Guarantor and the successors and assigns thereof, and shall inure to the benefit of the Administrative Agent and the other Secured Parties, and their respective successors, indorsees, transferees and assigns, until all the Obligations under the Credit Documents shall have been satisfied by payment in full, the Commitments shall be terminated and no Letters of Credit shall be outstanding, notwithstanding that from time to time during the term of the Credit Agreement and any Hedge Agreement the Credit Parties may be free from any Obligations. A Guarantor shall automatically be released from its obligations hereunder and the Guarantee of such Guarantor shall be automatically released upon the consummation of any transaction permitted by the Credit Agreement as a result of which such Guarantor ceases to be a Domestic Subsidiary of the Borrower. In connection with any such release, the Administrative Agent shall execute and deliver to any Guarantor, at such Guarantor's expense, all documents that such Guarantor shall reasonably request to evidence such termination or release. Any execution and delivery of documents pursuant to the preceding sentence of this Section 7 shall be without recourse to or warranty by the Administrative Agent.

8. Reinstatement. This Guarantee shall continue to be effective, or be reinstated, as the case may be, if at any time payment, or any part thereof, of any of the Obligations is rescinded or must otherwise be restored or returned by the Administrative Agent or any other Secured Party upon the insolvency, bankruptcy, dissolution, liquidation or reorganization of the Borrowers or any Guarantor, or upon or as a result of the appointment of a receiver, intervenor or conservator of, or trustee or similar officer for, the Borrowers or any Guarantor or any substantial part of its property, or otherwise, all as though such payments had not been made.

9. Payments. Each Guarantor hereby guarantees that payments hereunder will be paid to the Administrative Agent without set-off or counterclaim in Dollars at the Administrative Agent's Office.

10. Representations and Warranties; Covenants.

(a) Each Guarantor hereby represents and warrants that the representations and warranties set forth in Section 8 of the Credit Agreement as they relate to such Guarantor or in the other Credit Documents to which such Guarantor is a party, each of which is hereby incorporated herein by reference, are true and correct, and the Administrative Agent and each other Secured Party shall be entitled to rely on each of them as if they were fully set forth herein.

(b) Each Guarantor hereby covenants and agrees with the Administrative Agent and each other Secured Party that, from and after the date of this Guarantee until the Obligations under the Credit Documents are paid in full, the Commitments are terminated and no Letter of Credit remains outstanding, such Guarantor shall take, or shall refrain from taking, as the case may be, all actions that are necessary to be taken or not taken so that no violation of any provision, covenant or agreement contained in Section 9 or 10 of the Credit Agreement, and so that no Default or Event of Default, is caused by any act or failure to act of such Guarantor or any of its Subsidiaries.

11. Authority of Agent. Each Guarantor acknowledges that the rights and responsibilities of the Administrative Agent under this Guarantee with respect to any action taken by the Administrative Agent or the exercise or non-exercise by the Administrative Agent of any option, right, request, judgment or other right or remedy provided for herein or resulting or arising out of this Guarantee shall, as between the Administrative Agent and the other Secured Parties, be governed by the Credit Agreement and by such other agreements with respect thereto as may exist from time to time among them, but, as between the Administrative Agent and such Guarantor, the Administrative Agent shall be conclusively presumed to be acting as agent for the Secured Parties with full and valid authority so to act or refrain from acting, and no Guarantor shall be under any obligation, or entitlement, to make any inquiry respecting such authority.

12. Notices. All notices, requests and demands pursuant hereto shall be made in accordance with Section 14.2 of the Credit Agreement. All communications and notices hereunder to each Guarantor shall be given to it in care of the US Borrower at the US Borrower's address set forth in Section 14.2 of the Credit Agreement.

13. Counterparts. This Guarantee may be executed by one or more of the parties to this Guarantee on any number of separate counterparts (including by facsimile or other electronic transmission), and all of said counterparts taken together shall be deemed to constitute one and the same instrument. A set of the copies of this Guarantee signed by all the parties shall be lodged with the Administrative Agent and the US Borrower.

14. Severability. Any provision of this Guarantee that is prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective to the extent of such prohibition or unenforceability without invalidating the remaining provisions hereof, and any such prohibition or unenforceability in any jurisdiction shall not invalidate or render unenforceable such provision in any other jurisdiction. The parties hereto shall endeavor in good-faith negotiations to replace the invalid, illegal or unenforceable provisions with valid provisions the economic effect of which comes as close as possible to that of the invalid, illegal or unenforceable provisions.

15. Integration. This Guarantee represents the agreement of each Guarantor and the Administrative Agent with respect to the subject matter hereof, and there are no promises, undertakings, representations or warranties by the Administrative Agent or any other Secured Party relative to the subject matter hereof not expressly set forth or referred to herein or in the other Credit Documents.

16. Amendments in Writing; No Waiver; Cumulative Remedies.

(a) None of the terms or provisions of this Guarantee may be waived, amended, supplemented or otherwise modified except by a written instrument executed by the affected Guarantor(s) and the Administrative Agent in accordance with Section 14.1 of the Credit Agreement.

(b) Neither the Administrative Agent nor any other Secured Party shall by any act (except by a written instrument pursuant to Section 16(a) hereof), delay, indulgence, omission or otherwise be deemed to have waived any right or remedy hereunder or to have acquiesced in any Default or Event of Default or in any breach of any of the terms and conditions hereof. No failure to exercise, nor any delay in exercising, on the part of the Administrative Agent or any other Secured Party, any right, power or privilege hereunder shall operate as a waiver thereof. No single or partial exercise of any right, power or privilege hereunder shall preclude any other or further exercise thereof or the exercise of any other right, power or privilege. A waiver by the Administrative Agent or any other Secured Party of any right or remedy hereunder on any one occasion shall not be construed as a bar to any right or remedy that the Administrative Agent or any Secured Party would otherwise have on any future occasion.

(c) The rights, remedies, powers and privileges herein provided are cumulative, may be exercised singly or concurrently and are not exclusive of any other rights or remedies provided by law.

17. Section Headings. The Section headings used in this Guarantee are for convenience of reference only and are not to affect the construction hereof or be taken into consideration in the interpretation hereof.

18. Successors and Assigns. This Guarantee shall be binding upon the successors and assigns of each Guarantor and shall inure to the benefit of the Administrative Agent and the other Secured Parties and their respective successors and assigns except that no Guarantor may assign, transfer or delegate any of its rights or obligations under this Guarantee without the prior written consent of the Administrative Agent.

19. Additional Guarantors. Each Subsidiary of the US Borrower that is required to become a party to this Guarantee pursuant to Section 9.11 of the Credit Agreement shall become a Guarantor, with the same force and effect as if originally named as a Guarantor herein, for all purposes of this Guarantee upon execution and delivery by such Subsidiary of a Supplement in the form of Annex B hereto. The execution and delivery of any instrument adding an additional Guarantor as a party to this Guarantee shall not require the consent of any other Guarantor hereunder. The rights and obligations of each Guarantor hereunder shall remain in full force and effect notwithstanding the addition of any new Guarantor as a party to this Guarantee.

20. WAIVER OF JURY TRIAL. EACH GUARANTOR HEREBY IRREVOCABLY AND UNCONDITIONALLY WAIVES TRIAL BY JURY IN ANY LEGAL ACTION OR PROCEEDING RELATING TO THIS GUARANTEE, ANY OTHER CREDIT DOCUMENT AND FOR ANY COUNTERCLAIM THEREIN.

21. Submission to Jurisdiction; Waivers. Each Guarantor hereby irrevocably and unconditionally:

(a) submits for itself and its property in any legal action or proceeding relating to this Guarantee and the other Credit Documents to which it is a party, or for recognition and enforcement of any judgment in respect thereof, to the non-exclusive general jurisdiction of the courts of the State of New York, the courts of the United States of America for the Southern District of New York and appellate courts from any thereof;

(b) consents that any such action or proceeding may be brought in such courts and waives any objection that it may now or hereafter have to the venue of any such action or proceeding in any such

court or that such action or proceeding was brought in an inconvenient court and agrees not to plead or claim the same;

(c) agrees that service of process in any such action or proceeding may be effected by mailing a copy thereof by registered or certified mail (or any substantially similar form of mail), postage prepaid, to such Guarantor at its address referred to in Section 12 or at such other address of which the Administrative Agent shall have been notified pursuant thereto;

(d) agrees that nothing herein shall affect the right of the Administrative Agent or any other Secured Party to effect service of process in any other manner permitted by law or shall limit the right of the Administrative Agent or any other Secured Party to xxx in any other jurisdiction; and

(e) waives, to the maximum extent not prohibited by law, any right it may have to claim or recover in any legal action or proceeding referred to in this Section 21 any special, exemplary, punitive or consequential damages.

22. GOVERNING LAW. THIS GUARANTEE AND THE RIGHTS AND OBLIGATIONS OF THE PARTIES HEREUNDER SHALL BE GOVERNED BY, AND CONSTRUED AND INTERPRETED IN ACCORDANCE WITH, THE LAW OF THE STATE OF NEW YORK.

IN WITNESS WHEREOF, each of the undersigned has caused this Guarantee to be duly executed and delivered by its duly authorized officer as of the day and year first above written.


ROCKWOOD SPECIALTIES INTERNATIONAL, INC.,
by	/s/ XXXXXXX X. XXXXXXX
	Name:	Xxxxxxx X. Xxxxxxx
	Title:	Assistant Secretary
ALPHAGARY CORPORATION,
by	/s/ XXXXXXX X. XXXXXXX
	Name:	Xxxxxxx X. Xxxxxxx
	Title:	Assistant Secretary
ADVANTIS TECHNOLOGIES, INC.,
by	/s/ XXXXXXX X. XXXXXXX
	Name:	Xxxxxxx X. Xxxxxxx
	Title:	Assistant Secretary
CERAMTEC NORTH AMERICA INNOVATIVE CERAMIC ENGINEERING CORPORATION,
by	/s/ XXXXXX XXXXXXX
	Name:	Xxxxxx Xxxxxxx
	Title:	President/CEO
CHEMETALL CHEMICAL PRODUCTS INC.,
by	/s/ XXXXXX X. XXXXX
	Name:	Xxxxxx X. Xxxxx
	Title:	President
CHEMETALL CORP.,
by	/s/ XXXXXX X. XXXXX
	Name:	Xxxxxx X. Xxxxx
	Title:	Vice President
CHEMETALL XXXXX CORP.,
by	/s/ X.X. XXXXXX
	Name:	X.X. Xxxxxx
	Title:	Vice President
CHEMICAL SPECIALTIES, INC.,
by	/s/ XXXXXXX X. XXXXXXX
	Name:	Xxxxxxx X. Xxxxxxx
	Title:	Assistant Secretary
COMPUGRAPHICS U.S.A. INC.,
by	/s/ XXXXXXX X. XXXXXXX
	Name:	Xxxxxxx X. Xxxxxxx
	Title:	Assistant Secretary

CYANTEK CORPORATION,
by	/s/ XXXXXXX X. XXXXXXX
	Name:	Xxxxxxx X. Xxxxxxx
	Title:	Assistant Secretary
ELECTROCHEMICALS INC.,
by	/s/ XXXXXXX X. XXXXXXX
	Name:	Xxxxxxx X. Xxxxxxx
	Title:	Assistant Secretary
EXSIL, INC.,
by	/s/ XXXXXXX X. XXXXXXX
	Name:	Xxxxxxx X. Xxxxxxx
	Title:	Assistant Secretary
XXXXX CHILE HOLDING COMPANY,
by	/s/ X.X. XXXXXX
	Name:	X.X. Xxxxxx
	Title:	Vice President
LUREX, INC.,
by	/s/ XXXXXXX X. XXXXXXX
	Name:	Xxxxxxx X. Xxxxxxx
	Title:	Assistant Secretary
OAKITE PRODUCTS, INC.,
by	/s/ XXXXXXX X. XXXX
	Name:	Xxxxxxx X. Xxxx
	Title:	Secretary
ROCKWOOD AMERICA INC.,
by	/s/ XXXXXXX X. XXXXXXX
	Name:	Xxxxxxx X. Xxxxxxx
	Title:	Assistant Secretary
ROCKWOOD SPECIALTIES INC.,
by	/s/ XXXXXXX X. XXXXXXX
	Name:	Xxxxxxx X. Xxxxxxx
	Title:	Assistant Secretary
ROCKWOOD PIGMENTS NA, INC.,
by	/s/ XXXXXXX X. XXXXXXX
	Name:	Xxxxxxx X. Xxxxxxx
	Title:	Assistant Secretary
RS FUNDING CORPORATION,
by	/s/ XXXXXXX X. XXXXXXX
	Name:	Xxxxxxx X. Xxxxxxx
	Title:	Assistant Secretary

RW HOLDING CORP.,
by	/s/ XXXXXXX X. XXXXXXX
	Name:	Xxxxxxx X. Xxxxxxx
	Title:	Assistant Secretary
XXXXXXXXXX CORPORATION,
by	/s/ XXXX XXXXXXX
	Name:	Xxxx Xxxxxxx
	Title:	Vice President Plastics & Coatings Market
SOUTHERN CLAY PRODUCTS, INC.,
by	/s/ XXXXXXX X. XXXXXXX
	Name:	Xxxxxxx X. Xxxxxxx
	Title:	Assistant Secretary
SOUTHERN COLOR N.A., INC.,
by	/s/ XXXXXXX X. XXXXXXX
	Name:	Xxxxxxx X. Xxxxxxx
	Title:	Assistant Secretary
CREDIT SUISSE FIRST BOSTON, acting through its Cayman Islands Branch, as Administrative Agent
by	/s/ S. XXXXXXX XXX
	Name:	S. Xxxxxxx Xxx
	Title:	Director
by	/s/ XXXXX XXXX
	Name:	Xxxxx Xxxx
	Title:	Associate

ANNEX A
TO THE GUARANTEE

SUBSIDIARY GUARANTORS

AlphaGary Corporation
Advantis Technologies, Inc.
CeramTec North America Innovative Ceramic Engineering Corporation
Chemical Specialties, Inc.
Chemetall Corp.
Chemetall Chemical Products Inc.
Chemetall Xxxxx Corp.
Compugraphics U.S.A. Inc.
Cyantek Corporation
Electrochemicals Inc.
Exsil, Inc.
Xxxxx Chile Holding Company
Lurex, Inc.
Oakite Products, Inc.
Rockwood America Inc.
Rockwood Specialties Inc.
Rockwood Pigments NA, Inc.
RS Funding Corporation
RW Holding Corp.
Xxxxxxxxxx Corporation
Southern Clay Products, Inc.
Southern Color N.A., Inc.

ANNEX B TO THE
GUARANTEE

SUPPLEMENT NO. [ ] dated as of [ ], to the Guarantee dated as of July 30, 2004, among ROCKWOOD SPECIALTIES INTERNATIONAL, INC., a Delaware corporation ("Holdings"), each of the subsidiaries of ROCKWOOD SPECIALTIES GROUP, INC., a Delaware corporation (the "US Borrower") listed on Annex A thereto (each such subsidiary individually, a "Subsidiary Guarantor", and, collectively, the "Subsidiary Guarantors"; the Subsidiary Guarantors and Holdings are referred to collectively as the "Guarantors") and CREDIT SUISSE FIRST BOSTON, acting through its Cayman Islands Branch, as administrative agent (in such capacity, the "Administrative Agent") for the lenders to the Borrowers (the "Lenders") from time to time parties to the Credit Agreement referred to below.

A. Reference is made to (a) the Credit Agreement dated as of July 30, 2004 (as amended, supplemented or otherwise modified from time to time, the "Credit Agreement"), among Holdings, the US Borrower, Rockwood Specialties Limited, a company incorporated under the laws of England and Wales, the Lenders from time to time party thereto, the Administrative Agent and UBS Securities LLC and Xxxxxxx Xxxxx Credit Partners L.P., as co-syndication agents (in such capacities, the "Co-Syndication Agents").

B. Capitalized terms used herein and not otherwise defined herein shall have the meanings assigned to such terms in the Guarantee (or, if not defined therein, in the Credit Agreement).

C. The Guarantors have entered into the Guarantee in order to induce the Administrative Agent, the Co-Syndication Agents and the Lenders and the Letter of Credit Issuer to enter into the Credit Agreement and to induce the Lenders and the Letter of Credit Issuer to make their respective Extensions of Credit to the Borrowers under the Credit Agreement and to induce one or more Lenders or Affiliates of Lenders to enter into Hedge Agreements with the Borrowers. Section 9.11 of the Credit Agreement and Section 19 of the Guarantee provide that additional Subsidiaries may become Guarantors under the Guarantee by execution and delivery of an instrument in the form of this Supplement. Each undersigned Subsidiary (each a "New Guarantor") is executing this Supplement in accordance with the requirements of the Credit Agreement to become a Guarantor under the Guarantee in order to induce the Lenders and the Letter of Credit Issuer to make additional Extensions of Credit and as consideration for Extensions of Credit previously made.

Accordingly, the Administrative Agent and each New Guarantor agrees as follows:

SECTION 1. In accordance with Section 19 of the Guarantee, each New Guarantor by its signature below becomes a Guarantor under the Guarantee with the same force and effect as if originally named therein as a Guarantor and each New Guarantor hereby (a) agrees to all the terms and provisions of the Guarantee applicable to it as a Guarantor thereunder and (b) represents and warrants that the representations and warranties made by it as a Guarantor thereunder are true and correct on and as of the date hereof. Each reference to a Guarantor in the Guarantee shall be deemed to include each New Guarantor. The Guarantee is hereby incorporated herein by reference.

SECTION 2. Each New Guarantor represents and warrants to the Administrative Agent and the other Secured Parties that this Supplement has been duly authorized, executed and delivered by it and constitutes its legal, valid and binding obligation, enforceable against it in accordance with its terms.

SECTION 3. This Supplement may be executed by one or more of the parties to this Supplement on any number of separate counterparts (including by facsimile or other electronic transmission), and all of said counterparts taken together shall be deemed to constitute one and the same instrument. A set of the copies of this Supplement signed by all the parties shall be lodged with the US Borrower and the Administrative Agent. This Supplement shall become effective as to each New Guarantor when the Administrative Agent shall have received counterparts of this Supplement that, when taken together, bear the signatures of such New Guarantor and the Administrative Agent.

SECTION 4. Except as expressly supplemented hereby, the Guarantee shall remain in full force and effect.

SECTION 5. THIS SUPPLEMENT AND THE RIGHTS AND OBLIGATIONS OF THE PARTIES HEREUNDER SHALL BE GOVERNED BY, AND CONSTRUED AND INTERPRETED IN ACCORDANCE WITH, THE LAW OF THE STATE OF NEW YORK.

SECTION 6. Any provision of this Supplement that is prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective to the extent of such prohibition or unenforceability without invalidating the remaining provisions hereof and in the Guarantee, and any such prohibition or unenforceability in any jurisdiction shall not invalidate or render unenforceable such provision in any other jurisdiction. The parties hereto shall endeavor in good-faith negotiations to replace the invalid, illegal or unenforceable provisions with valid provisions the economic effect of which comes as close as possible to that of the invalid, illegal or unenforceable provisions.

SECTION 7. All notices, requests and demands pursuant hereto shall be made in accordance with Section 14.2 of the Credit Agreement. All communications and notices hereunder to each New Guarantor shall be given to it in care of the US Borrower at the US Borrower's address set forth in Section 14.2 of the Credit Agreement.

SECTION 8. Each New Guarantor agrees to reimburse the Administrative Agent for its out-of-pocket expenses in connection with this Supplement, including the fees, disbursements and other charges of counsel for the Administrative Agent.

IN WITNESS WHEREOF, each New Guarantor and the Administrative Agent have duly executed this Supplement to the Guarantee as of the day and year first above written.


		[NAME OF NEW GUARANTOR]
		by

				Name:
				Title:
		CREDIT SUISSE FIRST BOSTON, acting through its Cayman Islands Branch, as Administrative Agent
		by

				Name:
				Title:
		by

				Name:
				Title:

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GUARANTEE

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