paint blisters

[guitarman]

I have a question for Mac or anyone else that can help me with a problem that I've just recently had. My wife is a -one stroke- paint artist and I apply the sealer to all her projects. I applied the sealer to her latest piece and it blistered the paint and It can't be sold in that condition. I used the same sealer as I've done on all her projects and she used the same paint (brand) as she has done on all her work. What could have caused the blistering? I don't need to keep messing up her beautiful work. I need some suggestions on what's happening. Thanks, David

I might need to add that this is on a clay flower pot.

[workin for wood]

I will take a stab/guess at this. Moisture inside the pot. I don't know if you put water in the pot, I'm guessing not, and I assume you sealed both sides. My guess though is the pot had some water in it, perhaps from being outside, or from washing it before painting. The moisture pushed up the paint as it escaped from in the pot. It's a plausible theory anyhow. If you washed the pot before sealing, that's a good idea because you want to seal or paint a clean surface. Perhaps then you should put the pot into the oven on lowest temp for an hour to remove water that is inside the clay?

[Neal Moore]

I agree with Jeff. If you have used the same paint and sealer with no problems in the past then either the terra cotta pot contained moisture or some other contaminant or the brush became contaminated before being used. I assume she uses acrylic so moisture should not have been a problem. Maybe it's an isolated incident and you just got a bad pot??

[guitarman]

Thanks Jeff and Neal for your input. I've about decided that I may have just gotton a bad pot. I'll try it again on another one and see. I say this because the pot has never been wet or even damp for that matter. It's a new pot and nothing has ever been in it. The temperature may have something to do with it. It's hotter than h### here right now and the temperature inside my shop is so hot during the day that I have to do my work in the mornings and at night after it cools down some. My shop doesn't have AC. I'm really thinking about installing it. Thanks again guys, David

[workin for wood]

Don't set your pots on the cement, they will soak up water like a sponge. You don't see the water, but cement always has water in it unless you live in the sahara desert, because it is in contact with the ground. This goes for wood storage, always at least 12" above cement. Humidity can be how water is getting in the pots as well. Perhaps store your pots in the house and don't take them out until ready to seal them. Once they have sealer on them, humidity is much less of a problem. Can't imagine a pot can be bad, other than cracked. I can only guess moisture/humidity or some other contaminate being a problem. Good luck. Don't just toss out the old pot, crush it up and toss it in the garden. Lots of good minerals in those clay pots.

[MacS]

Blistering, is usally caused by heat, it could also be caused by a "hot" solvent, which maybe the solvent reacting with the paintng material.

Could you tell me what the sealer is that your using, and how long was it dried, before you wife painted the picture with the acrylic paint, did she "thin out" the acrylic paint with water, or a thinning medium she buys or mixes herself.

[guitarman]

Hi Mac, thanks for your response. The sealer that I've been using is a spray sealer made by Plaid. It's an acrylic sealer that I buy from A.C. Moore and also from Micheal's craft stores. I've never had a problem before and I think you may have hit the nail on the head when you said heat or hot solvent. It's been so hot lately here and you got me to thinking that the sealer was probably pretty hot when I sprayed it on. Could that be it you think? Also, my wife didn't thin out the paint before hand. The part that did all the blistering was in the base layer of paint that I put on the pot to begin with before my wife did her painting on it. I hope I made that clear enough. Sometimes I don't explain things to clearly. Thanks again for your time. David

[MacS]

Hi David,

The acrylic colorants are a heavy paste as I am sure you know, in some cases, they contain colored clays that come from the earth, the clays are actually the base colors, without a "medium" to keep the pigments pliable as it is being applied to the work, high heat could definitely cause the colored paste pigmented colorant to prematurely crack.

David, in some cases, you will find that high "heat" will cure the "acrylics colorants" right inside there tubes, this "curing" also applies to other pigmented paste colorants like the "universal colors, oil colors, japan colors, and all water colors in tubes."

[MacS]

Hi David,

Did you know?

If you look at the color of the clay pots, and then look at a tube of acrylic "Burnt Sienna," you will see that both of these colors are the same, because they both come from "iron rich clays," these mined clays are then baked in ovens, and then they are pulverized into micron sized particles, that will become the pigmented paste colorant in side the tubes that your wife and other artist use for painting.

See, what you learn just from asking a question.

[guitarman]

Thanks Mac, I definitely can see what can be learned by just asking a question. I knew you were the man to ask and I appreciate your help as well as all the help from the others that gave me advice. I'll let you know how my next try is with the sealer. I've stored all my sealer supply's in the house for now because it's so hot. Maybe a cooler temp will make a difference. Thanks again, Mac, for all the advice. David