Can I Just Thin It More When It's Cold?

The Wet Edge, No. 012. Short field notes for coating crews.

Here's one we hear every fall: it's 45 degrees, the epoxy's moving like cold honey, so can I just add more thinner?

Short answer: only up to what the data sheet allows. Cold material is thick because it's cold, not because it's short on solvent. The data sheet names the thinner and the maximum amount, and that limit is there for real reasons.

Go past it and a few things happen. You may be over the VOC limit for your area. You need more wet film to hit the same DFT, which invites sags. And in the cold, solvent leaves the film slowly, so the extra thinner can stay trapped and slow down the cure you were already fighting.

The better fix is heat. Store the kits somewhere warm overnight and bring them out as you need them. Many data sheets list a minimum material temperature separate from the surface temperature, so check both. Tnemec's Series N69, for example, wants the material above 50°F before mixing, 60°F for best results, and caps thinning at 10% for air spray and 5% for airless, roller or brush.

And while you're at it, make sure the steel is still 5°F above the dew point, because cold material is only one of your cold-weather problems.

Bottom line

Thin to the data sheet limit and no further. Warm the material instead of watering it down, and check the steel temperature while you're at it.

Further reading: Tnemec Series N69 Hi-Build Epoxoline II. Standards: ASTM D4414.

Talk to a consultant. Questions on a job? Atlantic Coating Consultants supports contractors in PA, NJ, DE, MD, DC, WV and OH with product recommendations, field support and crew training. Call 484-644-5303 or email atlantic@tnemec.com.