Wednesday, March 7, 2007
Milk Paint pt.3
One of my favorite adages is "An expert is someone who's made every mistake in a given field". I may not have made all the finishing mistakes, but I've made enough! Milk paint is the simplest of finishes as long as you want from it what it wants to give. When you start insisting on different results is when the trouble starts. I have always strived for a subtle mottled finish that has a warmth that begs to be touched and seems as natural as the wood itself. Not an imitation of wood, but an enhancement.
This brings me to the last steps in my painting process. After the paint has dried thoroughly, I rub it with a grey scotchbrite pad to cut the grit on the surface. Be careful around the edges, the same pressure that barely affects a flat surface will burn through the paint on the edges exposing the wood underneath. A little of this looks nice and will certainly increase with use, but I like to leave it up to my clients to do this. Be careful on softwood seats, light rubbing with a worn scotchbrite will avoid leaving scratches. I rub and rub and rub and rub. When I am tired of the scotchbrite, I switch to 0000 steel wool and put on my respirator. The steel wool will bring the paint up to a lovely sheen. I am careful to eveny rub the deck at the back of the seat, the spindles are natural barriers to being thorough and require extra care.
Once I am happy with the overall finish, I ask myself the all important question, "Am I ready for oil?"
The oil is the point of no return. The milk paint will not stick to an oiled surface, any further paint work will require scraping back to bare wood and starting over. I have scraped many a seat in persuit of a fine finish. If you have a question about how the paint will look with oil on it but are not willing to commit, try applying some denatured alcohol. This will give a good idea of what you will get with the oil.
I mix 2 parts of boiled linseed oil, 1 part spar varnish and 1 part mineral spirits and apply liberally. Let it soak in and reapply to any parts that look dry. After about 30 minutes, or before it gets too tacky to remove, wipe off all the oil. Then wipe it off again, and 30 minutes later wipe it off again. Any oil left on the surface will leave shiny "hot spots" that look terrible and are near impossible to get rid of. The next day, another coat can be applied, but won't soak in as much so there is no need to be so liberal in applying. Subsequent coats are the same.
There is no magic to the oil mix. It must meet a few simple requirements. It must soak in (hence the thinning with mineral spirits), it must build up and dry (hence the spar varnish) and it must be able to be applied without drying too quickly (hence the linseed oil). The spar varnish also adds water resistance. I always tell my clients that the 4 coats that I apply are tender in the first few months but in time will gain a great resistance to water and wear. Later I'll touch on my techniques for layering colors.