Problem with paint 'pooling' on resin?

[Birdie]

I've had this problem a few times, thought I'd ask if anyone knows what the problems is

Occasionally when painting resin, I get little 'pool' spots - that's the best way I can escribe it. It doesn't seem to show up with the primer, appearing when the main coat is added. I suspect it may be something to do with improperly cured resin. I've sanded it back down to the base and repainted, but it happens again. Primer and paint is cellulose. Any thoughts?

 

[CPTRogers]

Did you wash off the release agent? That can cause the paint not to stick and want to stick together "pool". Maybe the agent is coming through the primer? Just a guess.

 

[Birdie]

It's from a one piece mold, no release agent.

 

[renaissance_man]

It's from a one piece mold, no release agent.

Even if no mold release was used, I'd always recommend giving any resin cast part a clean before painting to remove surface contamination that can cause the problems that you're now experiencing with painting.
Are you painting a piece you've cast yourself, if so was a polyurethane or polyester resin used?

 

[Birdie]

Yes, I cast it myself, polyurethane. I've sanded it back down again and given it a good scrub with soap and water, and am trying again. Fingers crossed

 

[Funky]

Did you wash off the release agent? That can cause the paint not to stick and want to stick together "pool". Maybe the agent is coming through the primer? Just a guess.

Great answer. I've had this problem often and it always seems to happen when I get in a hurry and don't wash the release properly. Lots of hot water and a mild scouring pas with Dawn dishwashing soap. Then I wait till it's fully dried and start painting with light coats (but I'm sure you already know this )

 

[Gixxerfool]

I like simple green as well. It looks more like a fish eye in these pics, but it's hard to tell. If you have it after a wash and right before you paint use an acry-sol type of solvent. It's great at cleaning oils that you may have missed.

 

[logan74k]

It does look sort of like extreme fish eye, some paints are more prone to this than others. Besides getting the part clean, you can try slowly building up the paint in thinner layers. Spray a mist coat that doesn't cover completely and let it sit for 5-10 minutes, then do your wet coat. If you spray a wet coat from the start this is much more likely to occur.

If you're using a gun another possibility is oil in your air lines - just put a filter on there.

 

[Birdie]

Thanks guys, I used both techniques - a good clean, followed by thinner applications of paint, and it seems to have solved the problem. So care, less haste :thumbsup

 

[Badgersbunk]

I've noticed if my primer is rustoleum and my paint is any other brand something similar happens.

 

[juliegrrl]

Yup I got this problem on some very expensive resin kits from a very well known manufacturer - no matter what I did it seemed. Ended up sanding - soaked in simple green then using a primer coat of very fast drying automotive primer which worked reasonably well. Still had to do it twice to some parts due to the primer pooling. Acrylics were just a total lost cause.

 

[minifig]

One common problem that people often overlook is that if you are using a condensation cure silicone, it will often leech alcohol for the first week after its cured. It can be overcome by just casting in the mould a few times ( these castings, if in a slower curing urethane can often be sticky), but I don't like doing this cos its wasteful and shortens mould life. Gentle post cure baking can also help, but to be honest i'd just rather let it sit and be patient.
Of course, if its not a condensation cure rubber this info is completely irrelevant!!!!!