small bubbles/holes - I need help with spray painting

D

digitalauge

New Member
Hello (please move the post, if this is wrong place. *sorry*)
sorry I can not find a solution on Google.
I am from Germany and do not know any German forums where I can ask that.
I would like to prime my PU resin parts with spray primert and always get these little holes/bubbles.
I clean all parts with silicone remover and isopropanol. But that does not help anything.
Don't know what i do wrong. Can someone please help me?
There are no holes/bubbles in the parts before i prime.
I think I read once that I first have to bake the plastic parts in the oven. Is that correct?
(I make the silicone molds and castings myself)

Thank You

20180226_170102_HDR.jpg
 
Did you surface the resin parts with bondo? Could be you're seeing holes from the surface of the model and they're not filling in with paint.
Other option is something could be leeching out of the part into your paint causing the pitting in the paint.
 
digitalauge said:
Hello (please move the post, if this is wrong place. *sorry*)
sorry I can not find a solution on Google.
I am from Germany and do not know any German forums where I can ask that.
I would like to prime my PU resin parts with spray primert and always get these little holes/bubbles.
I clean all parts with silicone remover and isopropanol. But that does not help anything.
Don't know what i do wrong. Can someone please help me?
There are no holes/bubbles in the parts before i prime.
I think I read once that I first have to bake the plastic parts in the oven. Is that correct?
(I make the silicone molds and castings myself)

Thank You

View attachment 798515
Click to expand...
I get that with temperate issues. Either taking a cold item outside and spraying in extreme humidity, or having the paint in the cold AC and bringing it out and spraying the piece outside in humidity. Make sure both the paint and piece you paint sit out in the paint area together for some time to acclamate to the same temperature. Also make sure to share paint cans really well and spray small thin coats. Too heavy of a spray can also cause issues like this. Build up thin coats.
 
digitalauge said:
No i don't use bondo ause I have not seen any holes.
"leeching out" can i bake the parts, before I paint it?
Click to expand...
I've never heard of putting resin parts in the oven, I'd think it would warp/melt them.
This is just personal experience, but I've had resin parts get those pin holes before and it was due to not properly cleaning the parts before I painted them. Could try soaking them in soap and water overnight to get all the release agent off.
 
There are bubbles in your resin just under the surface. The solvent in the paint melts the surface of the resin just enough to adhere to the resin but reveals the imperfections just under the surface. Try warming the moulds in the microwave for about 10-20 seconds and then cover your moulds with a light dusting of talc powder. The talc will allow the resin to flow smother and lessen the chance of getting bubbles. Also, when pouring the resin, pour quickly. Having a thin stream of resin going into your mould will increase the chance of bubbles, if possible, slam down the mould after your pour the resin to shake loose any bubbles. You have to do this as early as possible. The resin starts curing as soon as it's mixed. The longer you wait the thicker it will become and more difficult to dislodge bubbles.
Some members also use a pressure pot, but that will cost a bit.

TazMan2000
 
I think Taz is right. Your paint is exposing micro-bubbles in your casting. You can use automotive glazing putty for those tiny holes (or hobby spot putty if you have access).

It's different from Bondo-type body fillers. It has the consistency of toothpaste so you can work it into small holes, and it air dries like paint, rather than catalyzes. It's great for filling in small holes and scratches, but not for large holes or contouring like you would use Bondo. I often use it on top of Bondo to fill in the sandpaper scratches before painting.
 
Thank you all for youre tipps. Now i think too that the smal holes are in the casting and the spray paint melts and than i can see it and not befor.
I think a lot about a
pressure pot​
but ist not cheap -_-
I think for next i try some putty to fix it.
 
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