Maybe you’ve had this happen to you. It’s happened to me at least four times. By the fourth I had recognized the pattern and I blew the guy’s mind.
As I’ve pointed out many times, finishes targeted at amateurs and small shops are made difficult to understand by the poor and often inaccurate labeling from manufacturers. As a result, a lot of room is created for people to come up with their own concoctions that they may want to keep secret.
So every once in a while a guy (always a guy) would come into my shop with a furniture project for me to fix or finish. During a discussion he would mention that he knew a secret formula for a terrific finish that had been passed down in his family. The formula always turned out to be the same: boiled linseed oil, spar varnish and turpentine. One-third each.
I was amused each time because I knew this formula wasn’t so secret. I had come across it many times in the old finish books I had. The results it produces are no different than Watco Danish Oil.
Anyway, the fourth time a guy bragged to me about his family’s secret formula, I decided to have some fun. So when he told me that his formula was such a valued secret within his family that he couldn’t reveal it to me, I said, “I already know it.” And I listed the three one-third parts and watched his face go pale. I just laughed.
It’s always spar varnish! Why? I have no explanation for this, other than there seems to be some mystic (also, a lot of misunderstanding) about the word “spar.”
It’s also always turpentine, never mineral spirits. But this could be because the only thinner available at the time the secret formula got started was turpentine. Mineral spirits didn’t exist.
Just so you know, in case you haven’t thought about this, there’s no reason to use spar varnish or turpentine. The type varnish and type thinner won’t make any difference. The linseed oil determines the principal characteristic of this finish. It won’t dry hard, so all the excess has to be wiped off after each coat, and what remains should be allowed to dry at least overnight.
The way to tweak the formula would be to reduce the amount of oil a lot to increase the gloss a little, assuming you’re using a gloss varnish.