I thought tack rags were made from a combination of varnish and something else...?

BTW if anyone is thinking about making tack rags from boiled linseed oil I wouldn't. I use boiled linseed oil and varnish for finishing all the time. Any cloth that get's linseed oil on it must be sealed airtight after use or soaked in water, gotten rid of etc. right away. My soaked paper wipers go outside in a wire "composting" circle AWAY from the shop. I've added many cartons of towels to this pile over the past 5 years. It just keeps reducing itself. Once in awhile in the summer if the top gets wadded too tight it'll set itself on fire.[X(]

I've known of too many shops lost to spontaneous combustion of oily rags. This goes for Watco etc. Mine was one of them because of another woodworker in the same building I was in. Sorry for the preachy rant, but if this saves someone this nightmare it's worth it.