Oil based paints, including the one-part polyurethanes, and associated thinners and reducers, correctly used, emit modest amounts of volatile organic compounds (VOCs) to the air. Best practices for application of these paints will minimize but cannot eliminate these emissions – simply put, the VOC content dissipates to the atmosphere as the paint dries.
One way to help minimize the overall impact of painting with oil based products is to adopt procedures for brush cleaning that reduce the dissipation of VOCs to the atmosphere, that minimize spillage of solvents, and that do not discard used solvents. Here is how to accomplish that goal; you will also improve the quality of your work, extend the lifetime of your paintbrushes, and save money on brush cleaning costs.
As you continue reading, it will become apparent that the information presented in this post is intended for folks who will be painting with polyurethane/oil based paints on a recurring basis over a longer period of time. For occasional work, please consider an option. Many projects, especially indoor work, house siding and exterior trim, and marine applications not continuously exposed to sun or water, can be successfully completed using water based paint products. High quality products are available, and water cleanup is easy.
A few words on brushes – 1 1/2 inch and 2 inch wide quality brushes work well for most oil or water based paint projects – brushes with long non-tapered handles are more suitable for cleaning using this process, but any brush can be spun. YouTube brush spinning if necessary.
Materials needed for the brush cleaning kit: One 5 gallon plastic paint bucket with the carrying handle – tight fitting lid is preferred, four, + two spare 1 quart glass mason jars (the type with 2 part sealing lids), one 2 pound or so empty food can, one 1 gallon metal can of mineral spirits, clean rags, tape and markers. A significant quantity of mineral spirits is required going forward, but very little is consumed, and none is discarded. Mark four of the jars #1 through #4, and fill each with about 24 ounces of mineral spirits. Put lids on jars, insure these lids seal the jars. Set aside the rest of the mineral spirits and the spare jars. Work in a well ventilated area or outdoors.
Step #1: Set the 2 inch brush to be cleaned into the 2 pound empty food can. Add spirits from the #1 jar. You want to have as much spirits in the can as possible, but not so much that you will slosh spirits out while you are dunking the brush. Repeatedly dunk the brush all the way down to the bottom of the can, displacing the bristles down to the heel – you want to be sure all the paint in the brush has mixed with the spirits. The spirits will be dense in color from the paint.
Step #2: Rake the bristles against the top edge of the can to rake most of the spirits out of the brush, take the brush to the 5 gallon bucket, and, with the bristles as far down into the can as possible, spin the remainder of the spirits from the brush into the bucket. Set the brush aside, and carefully return the spirits from the can to jar #1.
Step #3: Repeat steps #1 and #2 for this same brush using jar #2 through jar #4 in sequence. Each jar, the spirits will be less dense in color from the paint, the spirits returned to jar #4, hardly any paint color at all.
Step #4: Pour the small quantity of spirits from the bucket into jar #1. Wipe the bucket with a rag and store the rag in the can. Put the 4 jars and the can in the bucket, put the lid on the bucket, store the bucket in a location suitable for paints and solvents – ready to go to the work site for the next painting session.
Over a short time, you can paint many coats of the same or similar colors and clean the paintbrushes simply using this kit and this process. If you regularly use deeply contrasting colors, 2 copies of jar #1 and possibly jar #2 may be required if you are working over a short time.
The reason this works so well over even a short time, and decidedly so over a few days or more is that the paint solids removed from the paintbrush during cleaning settle to the sides and bottom of the jars when left alone. So the spirits are effectively as new when poured from the jars into the can for the next use.
After many, many uses, the volume of spirits in all 4 jars will be lower, and the insides of jar #1 will be substantially coated with paint solids cleaned from paintbrushes. Relabel jar #1 to jar X, pour the remaining spirits from jar X into jar #2 and relabel jar #2 to jar #1. Relabel jar #3 to jar #2, jar #4 to jar #3, and make a new jar #4 from your spare jars and the remaining spirits from the metal one gallon can. You are back in the brush cleaning business. Discard jar X – no spirits are discarded. Smaller jars and smaller volumes of mineral spirits might be suitable for smaller projects and smaller brushes.
This information is provided free of charge even though it is worth plenty. No warranty of any kind is expressed or implied.