How to thin out craft resin

Resin thickens in cold conditions and can feel sluggish to pour, especially straight out of storage in a cool room. There's a safe way to get it flowing more easily, and a few common tricks that will damage your project. This guide covers both.

Why resin gets thick

Viscosity — how thick or runny a liquid is — is temperature-dependent. Colder resin and hardener are thicker and pour more slowly; warmer resin and hardener flow more easily. This is normal and doesn't mean anything is wrong with the product. For reference, here's how the different Craft Resin products compare straight out of the bottle at 25°C:

Product	Resin viscosity	Hardener viscosity
Arts & Crafts	1,600 CPS	up to 1,200 CPS
Table Top	10,000 CPS	2,000 CPS
Deep Pour	1,000 CPS	220 CPS

Table Top resin is noticeably thicker than Arts & Crafts or Deep Pour by design — it's formulated to self-level in a shallow coat rather than run off edges.

The safe way: warm it before mixing

The only method we recommend for thinning resin is gentle warming of the unopened bottles before you mix. Warmer resin and hardener flow more easily, measure more accurately, and mix together more evenly.

If your workspace or your bottles are cold (below 15°C), warm Part A (the resin) to around 30°C before mixing. A warm water bath works well for this: fill a sink or basin with warm — not hot — water, and stand the sealed, unopened bottles in it for several minutes until they feel warm to the touch. Dry the bottles off before opening them, since you don't want water anywhere near the resin.

Keep in mind that warming the resin also warms the reaction once you mix it, so your working time will run on the shorter side. Have your mould or surface ready before you mix so you're not scrambling once the resin is flowing.

Working in a warm room helps too. Ideal ambient temperature is 24-30°C for Arts & Crafts and 25-30°C for Table Top — a cold room will make even properly mixed resin feel stiffer than it should.

What not to do

• Don't add solvents. Acetone, denatured alcohol, mineral spirits, or any other thinning agent changes the chemistry of the resin-to-hardener ratio. The result is usually a resin that never fully cures — it stays soft, tacky, or sticky permanently, and there's no fixing it after the fact.
• Don't add water. Resin is not water-soluble. Water in the mix causes cloudiness, fisheyeing, and cure failure.
• Don't overheat the bottles. A microwave, direct flame, or very hot water can heat the resin unevenly or start it reacting inside the bottle, which shortens your working time before you've even started and can affect how long it stores afterward.

Step-by-step

1. Check the room and bottle temperature. If either is below about 15°C, plan to warm the resin first.
2. Warm the unopened bottles in a warm (not hot) water bath for several minutes, then dry them off completely.
3. Measure by volume, in the correct ratio for your product, exactly as you normally would — warming doesn't change the ratio, only how easily the resin pours and measures.
4. Mix promptly and thoroughly, then pour without delay, since warmed resin has less working time than resin mixed at room temperature.
5. Pour and finish your project while the resin is still flowing easily — this is when it self-levels and releases trapped air most readily.

Related articles

• Mixing Ratio — How to Measure Resin and Hardener Correctly
• Craft Resin Technical Specifications
• Bubbles — Why They Appear and How to Remove Them