You can definitely get all the oil and any dried stuff out with acetone however.Dangerous stuff — fumes! But works like a bomb. I also wash the brushes frequently in synthetic, odorless turp and wipe them dry dry dry with a rag while working because linseed oil is NOT what I want any extra of in my paint. It yellows and cracks. Only alkyd mediums will do. Vastly more permanent…

But I follow the acetone treatment with The Master’s Brush Cleaner and shape the brushes with my fingers so they dry with no bristles sticking out. I’ve found that only the finest sables and hog brushes can hold up to the rigorous cleaning.

No offense taken (I hope I didn’t offend anyone else!) Are you painting your sculpture?

About the sand, my wife and I are from the Pacific Northwest. She is very unhappy about any chemcials around the kids. I just use a little bit of sand to help pull excess paint off. The paint adheres to all the surfaces on the sand, then I clean with regular soaps. But I am not a painter really, mostly sculpture. So I don’t have the same worries you folks do.
Peace.

I remember always getting a headache cleaning my brushes with turpentine!

As a safety note on the linseed oil method, it is good to note that rags covered with linseed oil can be a fire hazard because linseed oil releases heat as it dries. Under special conditions, this can cause combustion, although I never use that much oil. But to be on the safe side, I always store the waste rags/paper towel in a metal container to avoid the (probably negligible) risk of spontaneous combustion from these items.

Yes of course, the brushes cannot be stored resting on their tips. One way is to have them on a slope, with the hairs resting in a well of oil. Another method is to tie the brushes together and have a stick longer than the brushes in the bundle, so that the brushes can stand vertically in a bottle without the hairs touching the bottom. Cennino seems to simply have the brushes laying flat in a box of oil, which is not so bad — you just have to wipe off the handle before using. In fact, this method has the advantage that you don’t get linseed oil drying between the wood and the ferrule, since the entire brush is submerged.

Turpentine followed by warm water and dish soap works pretty well, but it is an a lot of work compared to the linseed oil method. The other nice thing about the linseed oil method is that if you are in a hurry, you can just store your brushes without even cleaning them.

Paint thinner is a solvent, so long-term storage of brushes in it might be bad for the brushes. Long term storage in linseed oil does no harm. Also, thinner stinks. But for urethane paint you obviously don’t want to use linseed oil.

I think that the solvent allows the oil to penetrate deep into the brush, where you can never really get it out. This is one reason I think it is good to never let oil paint brushes stand in the air. It is not possible to really wash them of oil, and trying to is a lot of work.

I use fine sable brushes — often brushes made for water color — and I like da Vinci the best. To use sable for oil paint requires stiff fibers — Kolinsky sable is supposed to be among the best. These brushes are expensive. Storing them in oil, I can use them for a long long time. They wear down at the tips, but the hairs stay flexible don’t fuse inside the brush ferrule.

For bristle painting, I use some French brushes made from 10 year old hogs. This makes the fibers stiffer.

I find that high quality brushes last longer and give better performance for the work I do. If I care for them, they don’t cost me more than cheap brushes would, but I can do more with them.