Oil paint dries by oxidation – so if we wish to keep paint long-term, we have to find a way of stopping oxygen from getting to it. This is achieved by putting it into metal tubes. Tubing paint is relatively straightforward. It is a useful technique, not only if you make your own paint, but also if you need to re-tube paint from a damaged tube, or tube up your own convenience colour mixes.
The major art supply stores sell empty metal tubes suitable of filling with paint, in several different sizes. These are cylinders, open at the back end, generally made of aluminium and coated internally with an epoxy lacquer which is inert and stops the aluminium from reacting with the contents. They also usually have a ring of grey adhesive material on the last half-centimeter or so of the interior.
Empty tubes need gentle handling to avoid denting, and it is very important to avoid scratching the interior coating.
You will need:
Empty paint tubes (40, 60, or 120mls are convenient sizes)
two fairly small flat-bladed palette knives (3 inch blades).
Some solvent, preferably OMS, for cleanup
Lint-free paper towels/tissueslatex or nitrile gloves are useful.
Pliers, or canvas pliers are useful, but not essential.
A mug can be useful, to stand the tube up in, while working.
The process is simply to hold the tube open (back) end up, and gently scrape paint from a palette knife onto the edge of the tube so that it drops down into it. Tapping the cap-end of the tube gently on a table-top or on the palm of your hand a few times as you proceed, help to get the paint to go down, and release any air-bubbles. It is important not to scrape/damage the epoxy coating on the interior of the tube.
Fill the tube to about 1.5 to 2 inches from the top. (it is a messy mistake to try to over-fill it!). You may want to open the cap to check that paint is right down into the nozzle of the tube (Then put the cap back on!)
Start to squeeze the tube together a little above where you have filled it. What you are trying to do is squeeze the tube closed so that the paint fills it, without any air-space, but also without expelling any paint out of the end (that’s the tricky bit! – you will always end up pushing a little paint back out ).
Squeeze the back end flat. The end needs to be turned over 2 or 3 times and squeezed flat. This can be done by placing the flattened end of the tube down flat on a tabletop, putting the edge of a palette-knife along where you want it to fold, then smartly raising the tube to create the fold. Alternatively it can be folded over using pliers, or even better, wide-mouthed canvas pliers. Wipe the tube with a solvent dampened towel.