Pre Mixing paints and thinner

Thank you for all the help.  I almost bought some spare jars to go ahead and start, then I thought I should probably ask the question here before I start spending money.

ABARNE wrote:

As everyone said, thinned enamels go bad very quickly.  As for acrylics, I have discovered that they seem to last a lot better.  Although the paint settles into the bottom of the jar just like enamels, I find that with acrylics you can stir them up again with no ill effects.  I've experienced that using both ModelMaster Acryl and Tamiya acrylics when thinned using Tamiya thinner.  I still don't advocate pre-thinned acrylics, but you can ceratinly store thinned acrylics for quite some time. Andy

I can vouch for not pre-thinning acrylics.  I had a fair amount left over from a recent spraying, poured it into a jar and tried to use it about a month later and something was just not right about it.  I ended up pouring it out and mixed up a fresh batch.

As everyone said, thinned enamels go bad very quickly.  As for acrylics, I have discovered that they seem to last a lot better.  Although the paint settles into the bottom of the jar just like enamels, I find that with acrylics you can stir them up again with no ill effects.  I've experienced that using both ModelMaster Acryl and Tamiya acrylics when thinned using Tamiya thinner. 

I still don't advocate pre-thinned acrylics, but you can ceratinly store thinned acrylics for quite some time.

Andy 

MikeV wrote:

H3nav wrote: On a slightly different note, what if you custom mix paint, i.e., Tamiya, without introducing additional thinner. After reading MikeV's acylic post, most people seem to love Tamiya but the color range is limited when compared to MM enamels. I was thinking of premixing certain colors and sealing them for future use and thin them when ready for spraying.  E I don't think that would hurt at all as you are not introducing any thinning agent into the paint.

Unfortunately, that may not turn out to be the case, although it has a much better chance of success.

Each color of a particular line of paint may be formulated slightly differently than the others are. This is because some pigments react differently to one or more of the resins, solvents, or combinations thereof. (Metallics are an extreme case of this problem.) Mixing two different colors of the same brand and line of paint usually does not cause an immediate problem, but may not be stable for very long. Note the underline—there are startling and drastic exceptions. Some of you may recall the problem I had with a certain Tamiya green a little while ago. Once dried, it was impervious to Windex, isopropyl alcohol, ethyl alcohol, straight ammonia, and even lacquer thinner. Yet it was reduceable with isopropyl and/or water. The reason was that one of the pigments required a different resin than most of the Tamiya paints.

So I wouldn't recommend premixing colors by more than a few days.

H3nav wrote:

On a slightly different note, what if you custom mix paint, i.e., Tamiya, without introducing additional thinner. After reading MikeV's acylic post, most people seem to love Tamiya but the color range is limited when compared to MM enamels. I was thinking of premixing certain colors and sealing them for future use and thin them when ready for spraying.   E

I don't think that would hurt at all as you are not introducing any thinning agent into the paint.

On a slightly different note, what if you custom mix paint, i.e., Tamiya, without introducing additional thinner. After reading MikeV's acylic post, most people seem to love Tamiya but the color range is limited when compared to MM enamels. I was thinking of premixing certain colors and sealing them for future use and thin them when ready for spraying.

 

E

As Mike and Ross mentioned, it's not really a good idea.

I have premixed some Testors enamels for brushing, (it's not as thinned out as for spraying). It shortened the shelf life, but still lasted over a year. I thinned a few for washes, which is probably thinner than needed for spraying, and they lasted for months.

One thing to remember, we might be able to thin and clean up our enamel paints with paint thinner - a.k.a. mineral spirits, but it's not the solvent used when they produce the product.

Acrylics - I have no idea about them.

In the automotive industry we often had some paint left over after spraying. We would save it for awhile, but the shelf life wasn't too long, and we used the proper thinning agent. Should have seen some of the custom paintjobs on the toolboxes LOL.

I wouldn't premix the paint any farther ahead than a few days or at most a week if working with enamels. It's not that time consuming or hard to get the paint ready the day of spraying.

Don't do this with any paint. "Paint" is really a blend of resins, solvents, and pigments. These blends are balanced for stability in the can, among other things. Changing that balance, either by adding a new solvent or changing the amount of original solvent, may drastically affect long term behavior.

Thin your paints before spraying as necessary. Such thinned material can usually be stored for a few days, but then should be discarded.

Not a good idea with enamels as the paint will become unstable quickly.
With Acrylics I am not sure, I guess it depends on what you thin it with.