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Hi folks,

The worst day is behind us, but New England is still sweltering under the remnants of a heat dome.

I just wanted to ask if very hot and humid days are bad days to spray-prime miniatures outside or not. I've been waiting for the weather to cool out of caution, but realized wiser folk here might know definitively, so I thought I'd ask.

Hot and humid is real bad for spray prime. You really need to wait for the right moment before breaking out the rattle can.

You might be OK early/late in the day when it’s cooler, but be careful.

If you do get a bad prime, dump things into the paint stripper before it has a chance to fully cure. Save you some scrubbing.

I prime in Central Florida where it's always hot and humid.

I suggest braving the mosquitoes and priming in the early AM (3-5 AM).

Thanks for the advice, guys. I figured it probably wasn't a good idea, but it's always best to know for sure.

 Lathe Biosas wrote:
I prime in Central Florida where it's always hot and humid.

I suggest braving the mosquitoes and priming in the early AM (3-5 AM).

Getting up at 3 to 5 A.M. to spray prime? Lathe Biosas, I applaud your dedication to this hobby!

Can anyone scientifically explain what's wrong with priming hot/cold and humidity? In my region it's common to have humidity around 100 and temperature -30/+30 and I just prime with Vallejo primer and don't know something wrong.

kabaakaba wrote:
Can anyone scientifically explain what's wrong with priming hot/cold and humidity? In my region it's common to have humidity around 100 and temperature -30/+30 and I just prime with Vallejo primer and don't know something wrong.

When I spray/prime in too humid conditions it always results in a gritty surface.
Don't know the science behind it though, just the result.

In the heat the paint's adhesive might apply too fast. The paint might dry too fast and not adhere properly. This can give it a rough or blistering texture.

In the cold you have the opposite problem, and the paint will run and not layer properly.

If you can spray paint in these extremes with Vallejo... then keep using Vallejo haha.

I've found if I spray paint above 80F with high humidity (>50%) the spray paint will sometimes have a rough finish which really impacts the final paint job.

With spray varnishes I won't even bother unless I'm in the perfect range of 60-70F, with humidity between 30 and 40%. Just not worth the risk for me.

If in doubt i'd always spray an empty plastic carton/bottle at the same distance you plan to spray your models first. I

That way you can see if the spay goes on smooth or ends up lumpy/uneven

if it does you can try moving the can closer to the target (this can help if the spray is drying in the air when it's too hot)

I've never had an issue heat wise. Just with humidity.