Epoxy 101


  • Types of paints that can be used over System Three epoxies.

    We have found that most two-part water based paints and primers will work well over System Three epoxies. This includes acrylic and latex paints. We usually caution oil based or alkyd enamels and primers because they can contain driers that would react with the amines in our epoxies and can cause overall drying issues. Nonetheless, ALL paints should be tested by the user in a small area to ensure the results meets their expectations.

    Surface Preparation: Allow the epoxy to reach full cure before applying paint. Sand the surface of the epoxy with 150-220 grit and then wipe clean with denatured alcohol. 

  • How to decipher the batch number or code.

    The batch number is a 6-digit code that is associated with the product's manufacture date and is typically located on the bottom of the container. 


    Example: A product with the batch code #806141 was manufactured on June 14th, 2018.

  • How to fix orange peel in an epoxy coating.

    To help fix the appearance of orange peeling, please allow the existing epoxy to cure for about 48 hours or until hard enough for sanding. Block sand flat using 120-150 grit, vacuum sanding dust and wipe clean with denatured alcohol. You may then re-coat.

  • Are System Three products suitable for the fabrication or repair of a fuel or gas tank?

    Our coating resins and adhesives are resistant to diesel and aircraft fuel, but have limited resistance to gasoline. 

  • Get rid of bubbles in an epoxy coating.

    Two methods can be used to rid of bubbles in an epoxy coating:

    1. Roll and Tip Method: Bubbles that persist in the coating can be broken with a disposable bristle brush by lightly dragging it across the surface after rolling the product out. 

    2. Propane Torch: Quickly and lightly fan 6-8 inches above the uncured surface with a propane torch to accomplish bubble popping with greater speed. Avoid overheating an area as this could cause the epoxy film to pull away from the surface creating craters.

    NOTE: When coating a porous surface like concrete or wood, overheating to pop bubbles with a torch can cause the expansion of any air in the pores of the substrate and can make the bubble situation worse.

  • Which product, the Marine Spar Varnish or WR-LPU, offers better long lasting UV protection?

    WR-LPU offers better UV protection for epoxy resins and the surface underneath better than Marine Spar Varnish.  How much better depends on the length and severity of the exposure.  WR-LPU is a little more expensive, but being waterborne, is available anywhere in North America.  Spar Varnish contains VOC content, and its use is restricted in some areas, but if available, offers more ease-of-application and a cost savings over WR-LPU.

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Measuring & Mixing

  • Waxed paper cups.

    System Three's wax-lined paper cups are designed for measuring and mixing and not for storage. Most people will mix a volume as needed and apply it to the substrate well before it gets hot. Therefore, the wax coating is negligible. If a longer working time is needed, the contents should be poured into a wide containment such as a plastic paint tray. This will lengthen the pot life of the mixed epoxy and prevent it from getting too hot.  

  • How do I measure by volume vs by weight?

    Liquid products can easily be measured by volume; paste and solid products must be measured by weight. To measure by volume, the use of disposable cups with graduation marks on the side is adequate. Pour the Part A resin and the Part B hardener on top of each other, in the same container. For measurement by weight, a gram scale (for small batches), or a postal scale(for larger batches) is necessary.

  • Why did my epoxy heat up soon after I mixed it?

    Many of our clear epoxy adhesives, coatings, and laminating resins will heat up, or exotherm, if left in the mixing container too long because of the chemical reaction.

  • Epoxy got hot. What happened?

    Most of our liquid epoxy products need to be poured out soon after the two parts are mixed together to prevent premature curing, called "exotherm."



Adhesive Bonding with Epoxy

  • Best adhesive for bonding rubber.

    Gel Magic, T-88, and the G-2 Adhesives are all good options for bonding rubber. 

  • What materials will your adhesives bond together?

    System Three® epoxy resin adhesives will bond (glue) all woods, most metals, concrete, masonry, glass.  They will also bond some plastics like nylon and Mylar. Following a flame-treatment surface preparation, they will bond to many other plastics including polyethylene, polypropylene, polyvinyl chloride, acrylic and polycarbonate plastics. In addition, epoxy adhesives are the best choice for bonding dissimilar materials together. If epoxy bonds to Material A and to Material B it will bond the two materials to each other. The best thing to do is to try it and see for yourself.

  • What materials will adhere to epoxy surfaces?

    System Three® coating/laminating resins present easy-to-bond to surfaces.  When these surfaces are cured and prepared properly, nearly any film-forming coating or adhesive will bond well to them.  Follow the surface preparation directions on the product you intend to use over the top of the System Three epoxy product.

Product Safety


  • How do I clean up resin, hardener, and any uncured epoxy?

    Solvents such as lacquer thinner, denatured alcohol, and acetone may used for cleaning spilled resin and hardener. Lacquer thinner is the best choice for cleaning any mixed uncured epoxy. 

  • Do I need to wear a mask when working with your materials?

    Wearing an organic vapor respirator is necessary in the following situations:

    Spraying Silvertip Yacht Primer,

    Spraying WR-LPU

    Spraying, brushing, or rolling S-1 Penetrating Sealer

    Most of our products do not contain hazardous volatile materials, so wearing a vapor respirator is not necessary.  However, when sanding any of our products when cured, it is highly recommended you wear a dust mask or respirator, as any airborne dust particles can be irritating.

  • Are your products REACH Certified?

    Yes.  If you need documentation, please contact Technical Support, [email protected], and reference the specific product.

  • Are your products compliant for RoHS?

    Yes.  If you require documentation, please contact Technical Support, [email protected], and reference the specific product.

  • Safe for fish?

    Q:  Can you build an aquarium out of System Three products?

    A:  Yes.  You can build it out of wood and fiberglass using Silvertip™ or General Purpose™ Resin systems.  And then you can bond the parts together with one of our adhesives like Gel Magic or T-88.  But because our products have not been tested for aquatic leaching potential, you must then apply a finish to the completed unit that has been tested for its safety to fish.





Surface Preparation



  • Sanding guidelines for applying multiple coats of product.


    • Recoating or applying multiple coats of one of our 2:1 epoxy products (General Purpose, SilverTip, Clear Coat, MirrorCoat, etc.) can be done without sanding if done within 72 hours of the previous coat. Beyond 72 hours, sand the previous coat with no higher than 120 grit sand paper to ensure the next coat adheres or properly levels out. 
    • For S-1 Sealer and Cold Cure products, the recoat window is 24 hours. 
    • For all System Three adhesives (Quick Cure, T-88, Gel Magic, MetlWeld, etc.) sand in between coats for best adhesion if a second application is desired. Please follow all instructions on substrate surface preparation prior to applying System Three adhesives.
    • For fairing compounds, putty, and pastes, please allow to fully cure then abrade or sand if additional product is to be applied.


Product Application

EndRot Kit


Marine Spar Varnish

  • How do I thin down or lower the viscosity of the Marine Spar Varnish?

    The Marine Spar Varnish can be thinned with mineral spirits at up to 10-15% by weight.

  • Marine Spar Varnish Over Sanding Sealers

    System Three® Marine Spar Varnish can be used over some sanding sealers but it will depend on the formulation of the sealer. Most lacquer-based sanding sealers are not recommended because the sanding aids are wax-related. We recommend testing the varnish over any other sealers in a small section to ensure you get good adhesion between the two coatings.  Also, for future reference, the Spar Varnish does not require sanding in between coats if applied within 12-24 hours of the initial coat. 



  • RotFix Coverage.

    RotFix has an estimate coverage of 300-350 square feet per gallon. 

  • Can you use RotFix with other wood preservatives?

    While we haven't done extensive testing with wood preservatives besides System Three EndRot™ Borate Powder(sodium borate), we know that copper and zinc naphthenate are compatible with RotFix, when the preservatives are given at least 7 days to penetrate and dry.


  • What finishes are compatible over RotFix?

    We know that System Three® finishes, WR-LPU and Marine Spar Varnish 
    are compatible with RotFix™.  Nitrocellulose lacquer, waterborne finishes, and 2-part polyurethanes will work as well.  As far as oil and 1-part polyurethanes, you will need to test for compatibility.

  • RotFix as a paint primer

    RotFix Sealer is a great product for consolidating or hardening soft or rotted wood.  It's also useful as a general purpose wood sealer.  If you have wood to paint, and it's a little soft, but not rotted away to require a full repair,  Rot Fix epoxy sealer will act as a primer for paint.


Sculpwood Putty & Paste

  • Paint over Sculpwood.

    Once the Sculpwood putty/paste is hard enough to sand, both are capable of accepting any latex or water-based primers and paints. Oil based primers and paints can sometimes have drying issues so spot testing is recommended. Check for adhesion and overall drying. 

  • Can Sculpwood Putty or Paste be colored?

    Yes.  There are a few options:

    1)  Dry pigments can be added into the mixed products in any proportion. 

     2)  Liquid dyes or paint colorants can be added into the mixed at up to 2% by weight.

     3)  System Three® Epoxy Paste Pigments can mixed into the Part A at up to 10% by weight and then mixed 1:1 with the Part B.


  • Can you stain over Sculpwood Putty or Paste?

    Unfortunately, no.  The resin content of the products is high enough to effectively have them function somewhat as sealers, and the stain will not penetrate like it will into the bare wood.

    The suggested workaround is to mix dry pigments or house paint colorants into the paste or putty as you combine the Part A and B.  This can approximate the color of the stained wood around it.

  • How soon can SculpWood Putty be applied over the RotFix Epoxy?

    SculpWood Putty can be applied over the RotFix immediately after application.


  • How much Mirror Coat do I need for my project?

    Mirror Coat requires a total of 4.5 ounces per square foot (1/2 ounce for the seal coat and 4 ounce for the flood coat) of mixed resin and hardener. Therefore, you can multiply the square foot area of your project by 4.5 to calculate an estimate coverage. 

  • Can you apply MirrorCoat over previously varnished wood?

    Yes, Mirror Coat can be applied over previously varnished wood provided the varnish is sufficiently cured, clean, and sanded. 

  • Can fine scratches or defects be buffed or sanded out of your products?

    Yes.  System Three® offers a sanding and buffing kit for sale on the website.  Contents are shown below.  The video shows its use with Mirrorcoat®, but it also works well on WR-LPU and coating epoxies like Silvertip™.  Click on the image for detailed information and to purchase.



    A white paper literature piece can also be downloaded from the website here:

    Guide to Buffing and Polishing

  • What are the causes for fish-eyes or craters in Mirror Coat?


    From our experience, cratering or fish eyeing almost certainly indicate that one of three things occurred during your application:

    1. Insufficient drying and/or incompatibility with a stain or oil: Pre-testing is always recommended when using products from another manufacturer.

    2. Sanding too smooth can cause the epoxy to draw away from the surface. For example, sanding higher than 220 grit will make it difficult for the Mirror Coat to overcome the surface tension of the substrate. 

    3. Lack of coverage: We specify pouring the MirrorCoat at 4 oz/sq ft to allow enough coverage on the substrate. Any less will result in a lack of adequate coverage.


  • Can fine scratches be buffed or sanded out of Mirrorcoat?

    Yes.  System Three offers a sanding and buffing kit for sale on the website.  Contents are shown below.  The video shows its use.


    A white paper literature piece can also be downloaded from the website here:

    Guide to Buffing and Polishing

  • Mirrorcoat Heat Resistance/Temperature Tolerance

    The rule of thumb with cured Mirrorcoat® and how much heat it will tolerate is this:  If an object is not too hot to hold in your hand, you can set it directly on a Mirrorcoat surface which is completely (more than a week) cured.  If it is hotter, you must place a coaster or hot pad underneath the object.

    If you happen to put an object that is too hot on a Mirrorcoat surface, and it leaves a ring, the ring can many times be removed by passing a hairdryer back and forth over the affected area.




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  • How long before I can apply the WR-LPU over epoxy?

    Allow epoxy to cure at least 7 days at 70F or above before applying WR-LPU. Please see the Technical Data Sheet and the Paint Literature for more information on application. 

  • Shelf-life of System Three paints.

    System Three Silvertip Yacht Primer and WR-LPU Topcoat paints are guaranteed for 3 years from the date of manufacture. However, the shelf-life can be extended if stored well sealed above 50F. After 3 years, we recommend pre-testing a small sample prior to use. 


  • How do I thin down or lower the viscosity of the WR-LPU Topcoat?

    The WR-LPU Topcoat may be thinned with clean deionized or distilled water at up to 25%. 

  • Custom colors for WR-LPU

    WR-LPU waterborne polyurethane topcoat comes in 12 standard colors.  We will match any color sample you send us for an upcharge with a minimum order of 1 gallon.  Small 4 oz. samples of all 12 colors are available for a nominal charge from the website.  These can be intermixed in any proportions to obtain the color you want in order to have it matched.

  • I want to paint a design on my wood/epoxy paddleboard but I do not know what kind of paint to use or when to paint.

    You can paint your design under or over the epoxy coating.  If it's underneath, ordinary house paint will do.  If it's on top of the resin, we would recommend our WR-LPU.





  • How much epoxy do I need for my project?


    The tables below are a guide for estimating the amount of material recommended, depending on the end use.


    Coating Plywood/Hardwood

    Mixed resin/hardener coverage in square feet per gallon



     Seal Coat


     Build Coats





    400/4 mils





    400/4 mils

    Vertical Surface




    500/3 mils

    *Some soft wood materials will require 2 seal coats due to higher absorption.



    Mixed resin/hardener coverage in square feet per gallon





     Fill Coats

    4 oz. cloth





    6 oz. cloth





    10 oz. cloth





    24 oz. Biaxial Tape






    Adhesive Glue Lines








    Clamped Joints

    3-4 mils



    Vacuum Bagging

    8 mils



    Stapled Veneer

    20 mils







    Fillet Size

    1/4” X 1/4”

    1/2” X 1/2"

    3/4” X 3/4”

    1” x 1”

    Ounces Per Linear Foot









    Fairing Thickness



    1/4 “


    Ounces Per Square Foot








    U-TAH Cartridge*


    Bead Size

    1/8” x 1/8”

    1/4” x 1/4"

    3/8” x 3/8”









    Quick Cure 5 & 15




    *The units reflected are linear feet per cartridge.


    System Three® Resins, Inc.  P.O. Box 399, Auburn, WA 98071


    The information contained herein is based on the data available to us and is believed to be correct. However, System Three Resins, Inc. makes no warranty, expressed or implied, regarding the accuracy of these data or the results to be obtained from the use thereof. System Three assumes no responsibility for injury from the use of the product described herein.














  • Sanding guidelines for applying one System Three product over another
    • Recoating or applying one product on top of another for most of our 2:1 epoxies (General Purpose, SilverTip, Clear Coat, MirrorCoat, RotFix, etc.) can be done without sanding if done within 72 hours of the previous coat or product. Beyond that, sand the previous coat or product with 80-120 grit sand paper to ensure the next layer adheres to the previous one. 
    • For S-1 Sealer and Cold Cure products, sanding must be done after 24 hours. 
    • For all System Three adhesives (Quick Cure, T-88, Gel Magic, MetlWeld, etc.) putties or fairing compounds like QuikFair, please allow to fully cure then abrade or sand if additional product is to be applied.
  • Compatability of Mirrorcoat with Spar Varnish and WR-LPU

    If your Mirrorcoat® project is going outside, and will be exposed to a significant amount of sun, it needs to have UV protection.  We manufacture two products compatible with Mirrorcoat and are easily applied after simple surface preparation:

    Marine Spar Varnish




  • Epoxy Projects Outside.

    If your Mirrorcoat®, or any epoxy project is going outside, and will be exposed to a significant amount of sun, it needs to have UV protection.  The epoxy coating cannot be modified to provide this protection for itself.  So, for exterior applications, to keep your project looking its best for the long term, apply one of our UV-resistant coatings over the epoxy.  We manufacture two:

    Marine Spar Varnish




  • Use of T-88 for Repair of Certified Aircraft

    Although epoxy adhesives have never been expressly approved by the FAA for general use in certified aircraft repair, T-88 has been used for years on these repairs.  Please review the attached document(s) for guidance.

  • What is the best product for laminating longbows or recurve bows?

    Here are two excellent options(please follow the links for detailed information and pricing):

    1)  Use System Three® T-88, our original structural epoxy adhesive.  The viscosity is high enough so you don't need to be concerned about starving the joints.


    2)  Use Silvertip Gel Magic™, our non-sagging, gelled epoxy adhesive, with toughening technology to withstand increased vibration and impact resistance.


    Both will form permanent structural bonds when the parts are laminated in a jig.  The cured bows will still flex without cracking.

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