Alkyd Satin Impervo HVLP dull

alexh · 10-30-2011, 04:46 PM

Hi all,

I have been spraying alkyd SI with HVLP for quite some time (mostly built-ins or furniture) and I always get great results. I thin with mineral spirits to about 40 secs using a Ford cup.

I recently sprayed a large room full of trim but the sheen is very low compared to what I normally see. The painted surface feels very smooth so I don't dust is the issue. I then sprayed a second coat (after sanding lightly with 320), with as little thinning as possible and spraying as thick as I dare. The flow out was excellent - like glass. The room took about 5 hours to spray (I'm dead on my feet when done). I run a fan in the doorway to get rid of overspray.

I have been racking my brain trying to figure out what would account for the noticeable difference compared to earlier work and the only explanation I can come up with is the cure temps. We recently started getting much lower overnight temps here. I know when I sprayed it was about 70 degs. I finished about 6:00 pm and the temps were about low 60's. I can't imagine indoor temps went much below 60 overnight. I did see a weird effect with the painted surfaces after 8 hours or dry time - many areas had a shiny, wet look surface but when I touched it, it disappeared. I have never seen this before.

I know that SI is chameleon like with regards to sheen. Sometimes I spray an object and it almost looks like semi gloss (seems like this happens when temps are 80+ and I'm spraying in direct sun), othertimes it's satin at best. Of course over time even unthinned, brushed SI seems to always go to a satin although it takes longer than 1 week IMO.

Anyone know how much of a factor temps are with regards to alkyd SI sheen?

Thanks

Brushjockey · 10-30-2011, 05:17 PM

I really wouldn't think on at 70 with no lower than 60 would make much difference.
I have seen a difference when using deeper colors- starts out ( and sometime stays) glossier. More resins needed to carry the color.