I do use solvent while painting, both to clean my brushes and to slightly thin the paint for my underpainting. At first I used turpentine but within a short period of time switched to Gamsol, Gamblin's odorless mineral spirits. Gamsol has two safety features- a high flash point (reducing the risk of fire) and a slow evaporation rate (health safety). A slow evaporation rate is of some economic value as well. There are other odorless spirits on the market but I am not familiar with them. For a detailed discussion of safety issues related to solvents I recommend this article- https://professionalartistmag.com/using-solvents/
From time to time I am asked what I do with the gunk that forms on the bottom of my mineral spirits container/brush washer (I call it a turp can). Also, what do I do with used solvent. I use a medium size Holbein metal brush washer in the studio and a small one for my plein air backpack. Some of my friends prefer the extra large for studio work. At the time of this writing it appears that these containers are in short supply, but the company still posts all sizes so I assume they will continue to make them. These are pricey but worth it. The first can I purchased was inexpensive and one of the latches broke off almost immediately. The Holbein are reliably air tight as long as you keep the rubber seal out of the sun when you paint outside (i.e. put the lid in the shade or under something while the can is open).
Here is my procedure for reusing solvent. Skip this paragraph if you have the situation under control. After 2-3 sessions I pour the used solvent from my turp can into a glass jar with a tight fitting lid. Wearing gloves, I clean the thick paint residue on the bottom with paper towels, wiping until fairly dry. I put the paper towels in the trash to dry before discarding. I keep about 6 jars of settling solvent going in my storage cabinet. After cleaning the turp can I refill it with used spirits decanted from another jar that has completely settled. Because there is gradual evaporation with use, I have to add new mineral spirits to the can periodically, but I reuse the spirits indefinitely. I never dispose of solvent and I maximize its use. In 10 years I have yet to completely fill a jar with the solid residue, but once I do I will take it to a hazardous waste disposal station.
Below, I am decanting the spirits in a jar that has settled. The next image shows the gunk that has settled and become a solid.
And below are the newly decanted spirits. Very clear and ready for use. The level is low so I will add some new spirits.
Now for a housekeeping issue. With time solid material will build up in the can and more importantly on the piece inside used to wash the brushes. After long neglect mine recently looked like this:
I know, don't say it... the holes are almost plugged and the piece only fits into the can with difficulty. I soaked it overnight in Murphy Oil Soap with some added water. This was a tougher case than usual, but here is what it looks like now-
So I am back in business with a resolve to do this more often. It works very well, but if you wait as long as I did some elbow grease will be required. You can do this to keep the can nice and shiny, but I don't care about that.
Murphy soap is also great for soaking brushes with dried paint, and of course to clean hardwood floors. Unlike many products, I like the way it smells. It is carried in groceries and hardware stores.
I hope this was understandable and helpful. Thanks for reading!
Working Out the Kinks