i remember reading something about the dew point monkeying with how well our finishes lay out and wanted to see if i could get a refresher on what is happening and what to do about it.

our temps and humidity have been a little all over the place. we've been adjusting the amount of thinner we're using to compensate but we've been getting some bubbles/solvent pop of late. this is in contrast to our thin rates we have recorded when temps and humidity have been the same (just in other times of the year), so there seems like something else going on.

we're spraying 2k urethane and are using a medium thinner (not retarder).

When we have bubbles and solvent pop we use a little retarder to allow solvent to escape before top coating closes up.

Humidity makes a difference with lacquers more than most finishes, since
I switched to conversion varnish I've never
had a problem, I prefer to spray on a rainy day
because I get cleaner finishes. Humidity actually
helps a catalyzed finish to harden.
For lacquers, use automotive grade reducer to thin, works much better.
Most lacquer thinners today are reconstituted junk.

if your using 2k finishes and getting solvent pop you may be applying to much coating... viscosity is too thick or you need to retard the finish a bit to allow the air to escape before it skins over...... if your shooting over a particularly open pore wood you may need to reduce further and try lighter coats in the beginning so you don't get air entrapment...

i was looking for some pretty specific info as it relates to dew point - something i found a while ago in the archives. i just wanted more of an explanation.

i'm using the manufacturer's recommended reducers and thinners so i don't suspect an issue there. we started keeping a spray log, noting the humidity, temperature, our percentage of thinner or retarder, tip sizes, number of passes/coats, and initial and ending results. we did this in the fall and we've gone back to it often, and have found some good success using it.

shane - i'd posted a thread about in-line heaters and no one responded. would heating our 2k finish help here? obviously, the heat would thin it without reducing the solids and adding more chemicals that would need to evaporate (win-win). i'm just not sure if this is a great idea with 2k's. and i'm a little nervous about having pretty varying temps from the finish and wood being sprayed.

are you talking about the dew point in your compresssed air system or overall humidity in your shop

yes i have used binks and graco heaters on my 2k but i have them set at 80 degrees, sometimes a little higher and it helps but one thing i do that most mfg won't is that 10 minutes before i am done spray ing i shut off the heater so it can cool down slowly and there is enough residual heat to finish upmy project,

good luck herb j