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| Leave it to the pro. Michael Dresdner, a nationally known wood finishing and woodworking expert, has answered hundreds of common wood finishing questions in Varathane’s Q&A library to help you successfully complete your project. Click on a link to the left for help and solid advice. |
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| Q: A friend told me that if I were to clean the finish with alcohol, I should use ethyl instead of methyl alcohol.
A: They behave about the same, but ethyl alcohol is much safer to humans. With the exception of one brand, most denatured alcohol you buy at the home or hardware store is almost all ethyl alcohol. However, I must point out that I would not ever clean a finish with alcohol, especially if I did not know what it was, since it will remove shellac, some natural resin finishes, and will etch or severely damage most lacquers. The only finish you can safely clean with alcohol is a highly crosslinked high tech finish, and then there is no point to doing so. For almost all cleaning you can use mineral spirits, which will not harm any common finish beyond wax. |  | |
| Q: I have been asked to refinish an old pine door for a friend. In removing the old stain I found a tar-like substance which I presume is sap. It looks and smells like it. I’ve been able to get it off, but I will need to seal the wood before applying a new finish. Can I use shellac as a sealer for this purpose?
A: Yes, that’s exactly what you should use, but in order for the shellac to go under all finishes, you should use dewaxed shellac. The easiest and best form to buy that in is as Zinsser SealCoat, a ready to use clear primer made of dewaxed shellac. By the way, dewaxed shellac is, in fact, the only thing I have ever found that will seal sap, at least for a while. In the old days, thick shellac formulated for this usage was called ‘knotting’ because it was put over pine knots, which seem to frequently bleed sap. | | |
| Q: Despite a lot of hand sanding, I did not get out a lot of the planing machine chatter marks which gives a striped effect on some risers and parts of some treads. I shall have to buy a sanding machine and sand the new flight thoroughly before I start staining.
A: With or without a machine, the problem of planer makes has to do more with what grit you started with than how much sanding you did. The strategy behind sanding successfully without sanding too much is to understand exactly what the goal of each sanding step is, and which paper will achieve that goal. The first sanding is to remove machining marks and cutting tool marks, and that should be done with nothing finer than 80 grit, which will remove those marks quickly and completely. You then use 120 grit to remove the 80 grit marks, and 180 to remove the 120 grit marks. It’s sort of like the nursery rhyme about the old woman who swallowed the fly. The bottom line is that you don’t really need a machine to get out those marks, you merely need to do enough sanding with a coarse enough paper to start. | | |
| Q: I had a new pine door and window installed; one trimmed in mahogany the other in oak. Do I need to apply wood conditioner to just the pine before I stain or all the wood?
A: Use conditioner just on the pine. The other two woods will not require wood conditioner. Both mahogany and oak stain very nicely without any modification. |
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