CPE Lab

System Three S-1 Sealer + Lacquer Thinner

DIY alternative to Smith & Co. CPES Warm Formula • Canada-friendly

⚠️ SAFETY FIRST – READ BEFORE MIXING

  • Use outdoors or in excellent ventilation. Organic vapor respirator REQUIRED.
  • Wear nitrile gloves, safety glasses, and old clothes.
  • Highly flammable solvents – NO flames, sparks, or smoking.
  • Keep away from children/pets. Dispose of rags safely to prevent spontaneous combustion.

Why This Works

System Three S-1 Sealer is a 50% solids penetrating epoxy (mixed viscosity ~42 cps) designed for exactly the same job as CPES: deep wood stabilization and rot prevention. CPES Warm is thinner (~1 cps) because of higher solvent content. Adding standard lacquer thinner (fully compatible) gives you similar flow and penetration while keeping strong epoxy solids once cured. Thousands of Canadian boatbuilders and woodworkers already use this approach successfully.

Mixing Instructions

  • Measure S-1 Part A and Part B (1:1 by volume or use the exact gram weights below).
  • Mix thoroughly for 2–3 minutes (scrape sides/bottom).
  • Add the lacquer thinner and stir until completely uniform.
  • Use immediately (pot life ~24 hours at room temp).
  • Flood-apply thin coats to wood — keep flooding until it stops soaking fast. 2–4 coats typical.

    • Batch Recipes by Weight (½ oz – 2 oz total batches)

    S-1 mix ratio is 100:94 by weight (Part A : Part B). Weights calculated for the total final batch size you requested using manufacturer data and typical lacquer thinner density. Use a digital gram scale for best accuracy. Start with the 20% thinner column.

    20% Lacquer Thinner (Recommended Starting Point – great balance)

    Batch Size (total final mix) Part A (g) Part B (g) Lacquer Thinner (g) Thinner (ml approx)
    ½ oz 6.0 5.7 2.0 2.5
    1 oz 12.0 11.3 3.9 4.9
    1½ oz 18.0 17.0 5.9 7.4
    2 oz 24.1 22.6 7.9 9.9

    25% Lacquer Thinner (Thinner mix – closer to CPES Warm flow)

    Batch Size (total final mix) Part A (g) Part B (g) Lacquer Thinner (g) Thinner (ml approx)
    ½ oz 5.8 5.4 2.4 3.0
    1 oz 11.6 10.9 4.7 5.9
    1½ oz 17.3 16.3 7.1 8.9
    2 oz 23.1 21.7 9.5 11.8

    Tip: Round to your scale’s nearest 0.1 g. Measure thinner by weight for precision or by ml syringe. Always test penetration on scrap wood identical to your project and adjust % thinner on the next batch if needed.

    Application & Tips

    • Warm the wood slightly with a heat gun first for even deeper penetration.
    • Multiple thin flood coats every 10–30 seconds until it stops soaking quickly.
    • Recoat within 24 hours (no sanding needed). Full cure in 7 days.
    • Topcoat with paint/varnish as usual.
    • If you want zero thinning hassle, try straight S-1 or System Three Clear Coat (even lower viscosity, no thinner needed).
    Important notes: Heavy thinning reduces final epoxy solids, so use 1–2 extra coats to compensate. This is a popular DIY adaptation — not an official System Three recommendation (they suggest max 1–3% for brushability). Results are excellent for sealing/priming but test for your specific wood and conditions.