Questions about decanting paint

[Monty]

A number of years ago I bought a bunch of Testors rattle cans online because of rumors that most of the Testors model paint line was going away, and I wanted to have these on hand for future projects.  (These are shades such as Ford's pickup purple that aren't as common as their regular hobby shop lineup). Unfortunately, some are now showing the dreaded signs of seepage around the bottom, so I want to try and preserve the paint.

1) What are the best jars capable of taking the contents of an entire Testors can?

2) Many decant-and-spray articles I've read stress the need for the paint to "settle" after being decanted so it will airbrush better better.  Do I need to do this before capping the jar?  If so, how long?

3) How long will decanted Testors spray paint last in a jar?   

TIA for any additional info on this.  I'd get tossed of this board if I said what I really think about Testors cans and nozzles.  ?

[peteski]

1.  Well, look at how many fl. oz. is mentioned on the can and that is your answer (I would likely go a it larger). I never decanted an entire can.

2. The "settling" is not about being able to airbrush better.  You need to understand the chemistry.  The propellant gas in Testors spray paint is propane. But good portion of it is in a liquid state (just like in your grill's propane tank). As the pressure is released, some of it turns back to gas, keeping the can pressurized. When you rather abruptly release the pressure during decanting, some of the propellant remains in the liquid form for quite some time.   If you were to close the jar of decanted paint, the pressure would build up (lie it does in the can).  You need to keep the jar capped but unsealed to let the gas escape.  I usually gently swish the paint from time to time. When I do that I can see the paint foam up when the gas gets released.  How long, I have had decanted paint degas even couple of days later. Also, when decanting, the paint will foam up and turn very cold (as the propellant is released).  You would be better off decanting into a larger container, then once degassed, pour it into a smaller jar/bottle.

3. If the jar has an airtight seal and it is pretty full (not much air space over the paint), it will last as long as any other paint in a jar.  Spray paint is same as the stuff in the jars/bottles, except it is thinned.

Lastly, if some of the binder (the resin body of the paint) seeped out, the paint's chemical balance has changed, and it might not work as well, but reading online info seems that it still works well.

[customline]

I would like to confirm everything that Pete said and add my $00.02:  consider ambient temperature because it affects the pressure of the propellant. I decanted an almost-full can of Extreme Lacquer recently at around 90 F into a 8 oz. Ball jar, left the lid loose for a few hours then capped it tight and it stayed in the summer heat over night. The following day, I checked it to see if there was still pressure and there was a small release when I carefully cracked it open. Also, if you are intent on emptying a full can, you may need to warm (not "heat") up the can once or twice as the can cools and you notice the pressure dropping off. I use a hair dryer for that. I also use a pistol-grip thingie on the Testor's cans. It keeps my fingers free of paint and enables me to push the valve down which I could not do otherwise . Very helpful ?

The first time I decanted, I used a very small jar and capped it tight immediately.  I got a big surprise when I opened it later. The paint foamed out of the jar and all over me. I should have known better. ?

[mrm]

I airbrush a lot of spray can paint. Anything from Tamiya primer (and no, it's not the same when bought in a jar) to Walmart Rustoleum paint for garden furniture to automotive lacquers. And I have never felt the need to decant and store the paint outside its spray can. The absolutely best way to store it is in its metal spray can container. I don't decant any time before I use it. I have a big box of simple waxed paper shot cups. It's like $5 for a 100, 300? I don't know, something like that. Every time I need to use a color, I spray it in from the can into the cup. I swirl it a little to gas it out and pour it straight into my airbrush cup. Sometimes if paint is very gassy, like some Tamiya paints, it will literally look like it is boiling in my airbrush. I watch it fizzle up and settle and then just spray it. Never had an issue. This way Its easier to organize my colors as they are just in spray cans and I can see the caps from a mile away and on the can I have name, serial numbers, everything. Why overcomplicate things, when they work just fine the way they are? 

Edited August 14, 2024 by mrm

[Bainford]

16 hours ago, mrm said:

Why overcomplicate things, when they work just fine the way they are? 

The OP's question concerns Testors spray cans, which apparently do not work just fine the way they are.

Edited August 14, 2024 by Bainford

[Rich Chernosky]

I decant and airbrush almost all of my spray paint.  Most of it is stored on a rack next to my paint booth.  I find the very small neck 2-3oz bottles the best. BTW a full 3oz spray can holds exactly 3oz of paint. I use baby jars for this while it de-gasses then transfer it to my bottles. There are two ways to decant spray paint. The easiest way is to take the spray nozzle and pry the center out. Insert a tube into the hole and spray into your chosen container.  If the can doesn't spray then it has to be punctured. An almost empty can has very little pressure left so this is not much of a problem. A full can....well that's different. In both cases do not shake the can. Lay it on its side and take a very sharp awl and very slightly poke a hole near the top. Fold over a paper towel and punch through that while squeezing the towel. Very slowly pull the awl out while releasing the pressure. The paper towel  will catch most of the extra paint. When it stops hissing you can open the hole more and then punch a hole through the bottom at an angle. Bend the awl backwards to create a rip in the can. Now you can pour the paint out. Open up the rip and squirt thinner in the can. There are solids that collect around the bottom of the can and the thinner and a stir stick will help get them out.  This takes some practice so start with an empty can first. There is still enough paint in an empty can to do a 1/24 car. The tube does not pick it all up.  I collect all the empty cans from my fellow modelers and have enough now for a lifetime.   I still buy paint though...go figure. 

[peteski]

5 hours ago, Rich Chernosky said:

A full can....well that's different. In both cases do not shake the can. Lay it on its side and take a very sharp awl and very slightly poke a hole near the top.

IF you don't shake the can, the pigment will be all settled on the bottom of the can. If you decant it without shaking it first (to mix the pigment back into the liquid), your paint will not work well.  That is why cans have the glass marble in them - to agitate the settled pigment back into the liquid part of paint.

[Rich Chernosky]

57 minutes ago, peteski said:

IF you don't shake the can, the pigment will be all settled on the bottom of the can. If you decant it without shaking it first (to mix the pigment back into the liquid), your paint will not work well.  That is why cans have the glass marble in them - to agitate the settled pigment back into the liquid part of paint.

Peter..you are right about that.  Some of the pigment does settle to the bottom...especially in older cans.  That is why I rip the can open  and stir that stuff back in with thinner. Most decanted sprays have to be thinned anyway.  BTW...for some unknown reason I save all those glass marbles.  I have a q

[Rich Chernosky]

Peter..you are right about that.  Some of the pigment does settle to the bottom...especially in older cans.  That is why I rip the can open  and stir that stuff back in with thinner. Most decanted sprays have to be thinned anyway.  BTW...for some unknown reason I save all those glass marbles. I have a quart soda bottle almost full of just the Tamiya ones.

[peteski]

Yes, the pigment settles down in cans of any age, just like it settles down in regular paint bottles. Actually it settles even quicker since the paint in spray cans is less viscous than in brushable bottled paints.  Flat paints have more pigment/flattening agent than gloss paints.  If you weren't reclaiming all that pigment, that would be like using bottled paint without stirring first.

I also save all those glass marbles. Not sure why, as they are too large to drop them in hobby paint jars.  Maybe I'm saving them in case when I lose my marbles?

[mrm]

9 hours ago, Bainford said:

The OP's question concerns Testors spray cans, which apparently do not work just fine the way they are.

I did not mean the spray cans working just the way they are. They do not. But they will store the paint better, safer and for longer than any other jar. And on top of that have a rattle ball that will mix it when you need to use it. What I meant was why overcomplicate the storage aspect. 

[Bainford]

2 hours ago, mrm said:

I did not mean the spray cans working just the way they are. They do not. But they will store the paint better, safer and for longer than any other jar. And on top of that have a rattle ball that will mix it when you need to use it. What I meant was why overcomplicate the storage aspect. 

I agree, except with Testors spray cans. The OP is experiencing a common problem with Testors cans whereby the product inside seeps out through the joints over time, likely degrading the paint inside. 

Edited August 15, 2024 by Bainford

[deuces wild]

Yeah, I bought 3 cans of Inca gold and all 3 leaked out..????

[Zippi]

Nice thread fellows. Do any of you guys thin the decanted paint or spray it as is?

[Bainford]

1 hour ago, Zippi said:

Nice thread fellows. Do any of you guys thin the decanted paint or spray it as is?

In most cases it sprays well as is. Sometimes a little added thinner is needed. Do a test spray to assess the need, but I find it generally sprays well as is.

[Rich Chernosky]

Since I spray a lot of older paint I find thinning is generally necessary. Newer paints like Tamiya will spray unthinned but I like to thin my last coat anyway.  Adding thinner will also help to gas out the  de-canted sprays.  The Testors laquer line in my collection is about the only ones that leak out the seam. I think it has to do with the run of cans Testor used at the time. I understand from my LHS that it was a problem through out the line.