Spray paint question.

[Michael Costa]

I'm painting construction grade lumber black using Krylon Fusion. The directions say "apply additional coats within 2 hours or after 48 hours." I had some things to do and missed the 2 hour mark by a few hours. Do I really have to wait 48 hours to give it a second coat? I'm in AZ the pieces were out in this dry climate all day. I plan on put a few coats of clear satin spray spar urethane on the pieces if that makes a difference.

Thanks in advance.

[Wayne Lomman]

Yes you do. Within 2 hours means the fresh coat will bite into the previous. After 48 hours it has cured enough that all the evaporation is done and you avoid blistering or poor adhesion. Coating with this condition in the instructions is enough to make me choose another product. Cheers

[Michael Costa]

Thanks Wayne. Out of curiosity, how long would it take to blister? There may or may not be a few pieces in the mix that didn't follow that 48 hour rule.

[Mike Hollingsworth]

Second coat will wrinkle the first coat unless you wait prescribed time.

[Michael Costa]

After the first coat dries, I do sand it with crumpled newspaper. It's my understand that's over 10,000 grit. The first coat is very smooth when I'm done and sits in the Arizona sun all day. I can't imagine any solvent in the paint remaining, but I'm not 100% sure. Would it blister right away? I have some pieces (not all) that I added a second coat to the next day. So far, so good. But I don't know if this blistering would start right away or take a week or two.

Would the same wait time apply before adding a spray on poly? Is it obvious I don't have any patience? Lol.

[Wayne Lomman]

Blistering is unpredictable. You either do it to the specification or cut corners and take your chances. Or alternatively, pick a paint that doesn't have the same restrictions. Cheers

[Mike Hollingsworth]

Would it blister right away?

If not in the first few minutes, you're good to go.

[Wayne Lomman]

If not in the first few minutes, you're good to go.

Sorry but this is not correct. Blistering requires full film formation to trap volatiles under the film. This can happen days and weeks later. Cheers

[Michael Costa]

48 hours has passed while I though about it so I'm good. Lol
I just needed to distract myself long enough.

[Mehwish Yati]

After the first coat dries, I do sand it with crumpled newspaper. It's my understand that's over 10,000 grit. The first coat is very smooth when I'm done and sits in the Arizona sun all day. I can't imagine any solvent in the paint remaining, but I'm not 100% sure. Would it blister right away? I have some pieces (not all) that I added a second coat to the next day. So far, so good. But I don't know if this blistering would start right away or take a week or two.

Would the same wait time apply before adding a spray on poly? Is it obvious I don't have any patience? Lol.

I know that with physical painting, if you apply a second coat after the first has started but not finished curing, you can pull up the first layer.


I imagine similar issues could arise with spray painting, where there is a distinct 'layer separation' between the first and second layers but the first layer is still in transition. For example, your second coat may dry first while insulating the first layer, which may shrink as it dries, resulting in your outer layer cracking or crumpling as its 'foundation' shifts.