Old Paint

[shiro_amada_jp]

In my inventory of model building supplies, I still have some old Tamiya paints that I would like to use. My problem is that the paint has solidified in their bottles. How do I make them usable again? Do I need to put thinner in them? Moreover, is it recommended to use old paint colors? (they're about 3-4 years in storage already)

[Catch22]

Well, you MIGHT be able to use it if you put some water in it, but I don't know if you'll have much luck.

[Airframes]

If it has totally solidified, without any sign of it being able to be penetrated or stirred, then it is almost certainly unusable. If, however, the addition of a small amount of water, or the correct thinners, allows some movement, it MIGHT be posible to stir long enough to re-mix the pigments and polymer (I presume that, being Tamiya, it is acrylic paint.), but, from your decription, I doubt it.
Generally, if a paint, enamel or acrylic, is still 'liquid', and can be stirred to blend the carrier, oils and pigments to give the appearance of the original colour/shade, then it doesn't really matter how old the paint is; it should still be usable. I have very recently used some enamel paint (Humbrol) that is at least 25 years old, without problems!

[muller]

Same here Terry, Hu63, they stopped making it years ago, that old Humbrol stuff has some shelf life!

[SoD Stitch]

Originally Posted by muller

Same here Terry, Hu63, they stopped making it years ago, that old Humbrol stuff has some shelf life!

I have found (at least with Testors Model Master line) that it depends on the color; some colors last for decades (I finally had to throw away my 25-year old bottles of Dark Tan and SAC Bomber Tan), whereas some only last for a few months unless you take them off the shelf on a regular basis (every few weeks) and stir them up (Insignia Red comes to mind).

And Airframes is right: if they've already set-up, they're no good anymore; no amount of paint thiner is going to "unharden" the paint, you just need to toss them and get a new ones.

[Airframes]

You're right SoD, some colours will harden quicker than others, due to the type of pigment. Enamel paints tend to last much longer in tins, as in the Humbrol and Revell paints for instance. Those paints in glass jars/bottles, will be affected by light, which slowly cures the paint, causing it to 'go off' quicker. If your paints are in glass bottles, which I believe Model Master are, it's a good idea to try to store them in a case or box, in darkness. This will slow the ageing process.

[SoD Stitch]

Originally Posted by Airframes

You're right SoD, some colours will harden quicker than others, due to the type of pigment. Enamel paints tend to last much longer in tins, as in the Humbrol and Revell paints for instance. Those paints in glass jars/bottles, will be affected by light, which slowly cures the paint, causing it to 'go off' quicker. If your paints are in glass bottles, which I believe Model Master are, it's a good idea to try to store them in a case or box, in darkness. This will slow the ageing process.

I did not know that. And, what's worse, I work under a 500W tungsten halide lamp that puts out a serious amount of light, so I'll bet I'm "curing" my paint a lot quicker than I should! I will defnitely "hide" them from now on!