Mulling paint

Making your own oilpaint is not particularly difficult, but most of the online demonstrations I have seen on how to do it, teach poor techniques which lead to either over-oily, or poorly-dispersed paint.

To hand-mull paint well, you will need:
a large glass muller
a glass slab
two small flat palette knives (not painting knives)
a teaspoon
a jamjar
some paper towels/tissues
white/mineral spirit

dry pigment powder
linseed oil (washed cold-pressed oil is good).
stand oil
beeswax paste in turpentine (buy commercially, or to make this, add minimal amount of turpentine, about 5%, to beeswax and allow it to stand with occasional stirring, in a closed jar. May take several days/weeks).

gloves and a face-mask suitable for very fine particulates.

Health and safety
Some pigments are toxic, but even the non-toxic ones need to be handled regarding them as a respiratory hazard. Our aim is to handle in such a way as not to create dust which disperses into the atmosphere or contaminates surfaces. Thus, we want still air conditions, and to dampen the powder at the earliest opportunity, minimising open handling of dry powder. It is perfectly possible to make oilpaint without making a mess.

For your first few attempts, though, I strongly advocate choosing a relatively innocuous pigment such as yellow ochre. We also want to monitor and control any dispersal of dry pigment into the work area, and have contingency plans for accidental spillage. Having a clean, clear work area for this is very desirable, and at the end of the process we damp-wipe the area surrounding our slab to monitor any pigment dispersal which has occurred. Try to avoid getting any paint or pigment onto your hands, and if you do, wipe them and any contaminated surface with a dampened paper towel so as to avoid spreading it.

The process of mulling paint properly is time-consuming and should not be rushed, so try to carry it out at a time where you are not going to be disturbed. Wear a mask while handling dry pigment. Wear gloves if desired, but working carefully you should be able to mull paint without getting it onto your hands. Gloves are a protection against spillage, not an excuse to work messily.

Process
1. Making a paste
The first step is to mix dry pigment and oil, to make a crumbly paste. Most people do this by putting the pigment out on the slab, but it is less messy to spoon it into a jamjar, add some oil, and then mix with a palette knife. It can be helpful to first add a few drops of white spirit into the container of dry pigment and allow it to sit, closed, for a while, to dampen the powder down very slightly. I generally use washed cold-pressed linseed oil to which I have added about 10% stand oil, and for slower-drying paints a few drops of L&B white courtrai dryer (1 drop per 10 ml of oil). For whites and blues I tend to use a mix of cold-pressed linseed and safflower oil, with some stand. One of the great advantages of mulling your own paint is that it gives you control over what the pigment is dispersed in – you can add resins or balsams or your own choice of oil.

The aim is to make a paste which is crumbly. If needed, add a little more dry pigment.

2. The actual mulling process
The first important thing to understand about mulling paint is that you are not grinding the paint. The aim is not to reduce the size of particles, but to break up any aggregates of particles and ensure that they are evenly coated with oil. In order to do this, every single particle of pigment has to undergo shearing forces between the muller and the slab. Just pushing around large mounds of paint with the muller achieves nothing.

I think of the slab as being divided into 3 areas. From left to right, these areas are for paste, mulling, and processed paint.

First, I transfer the crumbly paste onto the slab, and use a palette knife to ensure that it is reasonably evenly mixed. I place a small quantity of this into the centre, put the muller down over it, and rub back and forth a few times. The correct amount of material is that which will spread under the muller, but not go up the sides of the muller. For a large muller this is about 0.5-1ml.

After pushing it back and forth a few times, it can be felt to change and become less resistant. At this point I use a second palette knife to gently scrape the paint off the underside of the muller and from the surface of the slab, and deposit it on the right. Any material which has gone up the sides of the muller at all is scraped off with the first knife and mulled again. If you have got the consistency of the paste right, the paint should also be of a good consistency, and as thick as commercially-tubed paint. The entire pile of paste is processed in this manner.

If the paint is too runny at this point, more dry pigment is added and folded in with a palette knife, and then the mulling process repeated.

I then generally add about 1ml of beeswax paste per 50ml of paint, mix this in with a palette knife, and then remull. The purpose of this is that it prevents separation on storage. An alternative is to add a similar quantity of my fumed silica medium.

Each small lot of paint being mulled only needs to be rubbed for a few seconds, but the process is time-consuming due to its repetitive nature. I can mull enough paint for a 50-60ml tube in about an hour.

3. Tubing
The paint then needs to be tubed. I will deal with this as a separate post.

4. Clean-up
The final process is clean-up. I wipe down the muller, slab and knives with paper towels dampened with white spirit. I also damp-wipe the surrounding worktop area and inspect the towel for the presence of any pigment. It is perfectly possible to carry out the entire process without any paint getting onto your hands.