Wood Talk Online – #13

The AWFS Las Vegas show is this week so if you’re in the area stop by and say hi to Marc and Nicole at the Festool booth. And last but not least, since Matt couldn’t remember the type of steel to use in hand plane blades as asked in a voicemail by Vic the answer is “O1 steel”. You’ll have to probably do a search to find where to get it. Someone sent in a link for the “Win a Weekend with Norm Sweepstakes”. Matt also mentioned the Podcast Awards. Check it out and VOTE FOR US when the voting opens!

In this episode our two hosts attempt to answer a number of questions about finishes. So many woodworkers have questions and concerns about which finish to choose, what are the differences and why, why, why??

To get the show started off we have a question from Mike in St. Paul, Minnesota asking all of the above. Luckily for us Marc has taken the time to put together the following information which should be a good guide to help get everyone pointed in the right direction:
1. Evaporative finishes (lacquer, shellac) are usually less durable and scratch easier. They easily dissolve when exposed to the appropriate solvent, which make them easier to repair i.e. a lacquered table with a bunch of scratches can be repaired by simply coating the table with lacquer thinner. When applying these finishes each coat that is applied essentially melts into the previous layer, resulting in one single layer. 2. Reactive finishes (oil-based varnish, catalyzed lacquer) are more durable but they are harder to repair. Each layer of a reactive finish simply lies on top of the previous layer, thus rather than one single layer you have multiple layers making up the thickness.

Oils – one of the first finishes woodworkers learn to love is plain old oil. Usually linseed oil or tung oil. Oils absorb into the wood and polymerize into a relatively soft rubbery material, not a film finish.
Application- best applied by thinning with mineral spirits 50% and flooding the surface. Allow absorption for several minutes, then wipe off the excess. Check again in a few hours to see if oil has come back out of the pores, if so wipe again. Allow 16-24 hrs between coats. Advantages- dummy-proof application, non-offensive odor for most people and it gives the wood a sense of depth that is hard to replicate with other finishes. Disadvantages- very little protection, yellows the wood (linseed oil more so than tung oil), longer cure times. Re-application over time is often necessary to keep the wood looking new.

4. Varnishes – there are numerous types of varnishes and what generally makes them different is the type of resin they are made with. And they all may have different durability, working, and appearance characteristics. For instance, many people feel that a standard polyurethane has too much of a plastic look so they prefer a varnish made with a different resin (just for clarification, polyurethane is a type of varnish). Application- can be applied by brushing, wiping, or spraying (wiping and brushing being the most common). Advantage- very durable. Good heat, solvent, scratch resistance, and easy to apply. Disadvantage- can make wood look “unnatural” and plastic like, and can be difficult to repair.

5. Oil/Varnish Blends – really the best of both worlds. You get the easy application of an oil with the protection of a varnish. This is the finish would I recommend most woodworkers to focus on in the beginning. Advantage- easy to apply like oil, but we get the benefit of the varnish. Versatile finish because depending on the number of coats you add, you can go from a thin topcoat to a nice protective film. Disadvantage- May not be as protective as a straight varnish. Requires longer drying times than varnish. Requires more coats to build up the film.