I’ve read a lot of threads on here (and other places) about ways to keep pre-mixed paint fresh. Freezers, clove oil, foil, saran wrap, syringes, ice cube trays, water, etc..

Yet it seems that even when covered in wrap or foil or exposed to very little air, the paints still don’t last very long.

Why then are metal tubes so good at keeping paint fresh for years? I would have thought they’d still be a bit of air in there, or are they really that tight around the paint (even with a nearly empty tube)?

The probable reason is that when a metal tube is squeezed, and pressed flat, it does not have a tendency to “pop back” to its original form, as some plastic tubes tend to do.

Whenever a tube regains is original shape after it has been squeezed, it is an invitation for air to take the place of the previous paint.

There is really very little “air” that contaminates the paint remaining in metal tubes, either before, or after they are squeezed. By their very nature, some paints tend to polymerize because of their specific ingredients, and the introduction of air has very little to do with such hardening of paint in the tube. There is not much you can do to prevent such a hardening in the tube of these paints.

Anyway, “no air” is the general reason that metal tubes keep paint fresh as well as they do.

an aside to the basic problem; the brand of paint matters, since most brands manufacture paints to be combatible within series, drying-wise. i’ve kept a paper palette with mussini out on the porch for weeks, temp +10C to -10C. the series is somewhat regulated with siccative, fast drying, and the only loss was burnt umber.. it only lasted let’s say three days.

if still inclined to test, find an ice cube tray with lid; posit paint in then fill with water covering the paint, close with lid; into the fridge.

Original tubes were longer and thinner. They lasted longer. So modern manufacturers shortened and widened the tube so the paints dont last as long due to increased surface area inside the tube, making you buy more. Just a small point taken with a pinch of salt 🙀

what does the surface area inside a tube matter if the tube is non permeable to air?
why don’t large Wintons just dry up right there in their honking humomgous tubes with all that surface area?
When were tubes longer and thinner, back in 1920?
How do you know that they lasted longer back then?
data?
need a lot more than a pinch of salt for this one

what does the surface area inside a tube matter if the tube is non permeable to air?
why don’t large Wintons just dry up right there in their honking humomgous tubes with all that surface area?
When were tubes longer and thinner, back in 1920?
How do you know that they lasted longer back then?
data?
need a lot more than a pinch of salt for this one

There is no data. There is nothing written about it. Its just the conspiracy theorist in me. But the less surface area of a thinner tube(top) would suggest less oxidation in that part of the shaft 😖

Before aluminum became cheap, some early paint tubes were actually lead foil. Tin Foil was still used in cigarette packs until recently since tabacco and aluminum foil reacted. While cast zinc is brittle, they also used zinc foils for packaging. I think the old toothpaste tubes that came with a winding-key were zinc foil.

I have some unopened W&N oil paints in metal tubes of my mother’s that are still “squishy” that must be atleast 30 years old.