Tiny bubbles in paint

[MrMiles]

I wish i took a picture before sanding and respraying. I recently painted the chassis on my 1940 ford convertible kit. I primed it with tamiya primer and sprayed it with tamiya matte black. however I looked at it after a short time and found tiny bubbles in some parts of the paint. the only other time i had seen this was when i had painted outside and wind got onto the wet paint. 

 

However I painted this inside with no wind.

 

I sanded it out and respraying it seems to have fixed it but im curious if others had seen it and know what the cause is 

[espo]

The only time I have had this happen was with a paint can that had been siting for a long time and I didn't get the paint mixed enough before I used it. 

[TarheelRick]

Another possibility could have been contamination on the frame before painting. Maybe you didn't get it clean enough before painting. Just brain(?) storming here.

[AC Norton]

HUMIDITY WOULD BE THE ONLY THING I CAN THINK OF....I USE TAMIYA EVERYTHING FOR SPRAYS AND HAVE NOT SEEN THIS MYSELF.....ALL I CAN OFFER...ACE..

[MrMiles]

maybe i didnt shake it enough. i just got the can so im not sure how long it sat. 

[Plowboy]

Bubbles in paint are usually from holding the spray nozzle too closely to the part. The propellant gets injected into the paint and then has to escape.

[MrMiles]

10 minutes ago, Plowboy said:

Bubbles in paint are usually from holding the spray nozzle too closely to the part. The propellant gets injected into the paint and then has to escape.

 

 

this is probably it. i was holding it close to get the paint onto the side of a piece, so i was holding it closer than normal and at a weird angle. i didnt think of this at all.

 

[Pete J.]

Had that happen all to often with Tamiya rattle cans.  The problem is the propellent dissolved in the paint.  If you hold the can it too close and the spray it on too thick, the top layer flashes off(forms a skin) before the propellent can off gas completely.  This happens most often in corners.

  You can do several things to mitigate this.  First is to spray several thin layers.  That way the dissolved propellent doesn't have to off gas through a thick layer of paint.  The second is to heat the paint.  This makes the propellent much more active and it will off gas much more quickly. 

My prefered solution is to decant the paint and spray it through an airbrush.  When you decant the paint, you can see the issue you mentioned quite clearly.  When you put it in a jar, it will continue to bubble for several hours.  Never ever seal a jar of freshly decanted paint.  A friend of mine did that and then shook the jar the next day to mix the paint.  When he opened the jar, he instantly painted the entire room(and himself) with little green polka dots. 😆