The finish mix I use is equal parts Boiled Linseed Oil, Mineral Spirits and Polyurethane. This particular mix uses polyurethane with either a satin finish, semi‐gloss or high gloss for a shinier finish. I bought a gallon of the BLO and a gallon of the MS as they have really long shelf life and I just bought a quart of the polyurethane (approx. $18.00) as that doesn’t have as long of a shelf life. I mix mine in a 16‐fl.oz mason’s jar with the wide lid so it has a tight screw‐on lid.
Sand the wood all the way down to a 400‐grit finish. I usually start with 100, then 150, then 220, then 320 then 400. It seems like a lot of sanding but I think the end result is worthwhile.
For the application:
- Have three approx. 12″ x 12″ clean cotton rags available and use disposable latex gloves because it gets messy.
- Stir or shake the mixture in the jar until all the sediment on the bottom has been absorbed.
- Dip one rag completely in the mixture and wring out most of the excess liquid.
- Coat the wood surface liberally with the wet rag.
- Immediately take the second rag and wipe off the excess from the surface of the wood.
- Immediately take the third rag and wipe the surface of the wood again until it is all dry.
- You can carefully handle it after an hour or so, but it will not be cured so don’t grip it too tight. Look on all the surfaces and see if there is any blooming of the finish (you’ll know it when you see it, it is like small puddles on the finish). If there is any blooming, just wipe it off with the third dry cloth.
- Let it dry 24 to 48 hours between coats. Be patient and don’t apply the next coat before the existing surface is dry. If you apply the coats too quickly the surface will have a gummy feel that takes a long, long time to go away.
- Three or four coats is usually enough, but put enough on for your personal taste.
Basically, the way it works: the oil penetrates the wood and really shows off the grain and wood features, the polyurethane is to give the wood a hard coating and the mineral spirits is used to thin the liquids out and allows them to be spread easier and aid with the drying process. The mixture goes a long way because the coating is so thin, so a word of caution is don’t mix a large batch because it will go to waste between projects.
IMPORTANT: do not discard the used rags until they have fully dried – at least 24 hours. Lay them out flat, or over the edge of a trash can and wait a day to throw them out. Piling wet rags together can lead to spontaneous combustion.