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I have several old pieces of furniture that have issues with the existing finish. I would like to do a gentle restoration of these pieces while maintaining the original look. I am not sure if the finish is shellac, or some kind of other varnish.

How would I be able to tell what is there? Is there a way to test the finish to determine what it is?

  • Take a scraping and send to a lab for analysis. Though that's only if you have time and money to burn. – ratchet freak Apr 24 '15 at 19:55
  • The "issues with the existing finish" is a little vague. Although you've received some good advice already on how to ID certain finish types better answers could be provided if you supply some details about the condition issues you're seeing. – Graphus supports Monica Apr 25 '15 at 5:09
  • @Graphus I have a coffee table where it almost looks like the finish was melted and then smeared a bit on the top. It has a red finish on it which is reminiscent of a Chinese laquered box. – Jason Hutchinson Apr 30 '15 at 19:42
  • @JasonHutchinson, That could be coloured shellac. I doubt it's lacquer since that's incredibly stable. – Graphus supports Monica May 1 '15 at 7:30
  • It is quite possible, even probable that is more than one finish applied. For example, a very old piece may have vanish covered in shellac with wax on top! – ewm Jan 11 '17 at 22:48
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Since they are very old, they are most likely lacquer or shellac. As previously noted, test for shellac with DNA, lacquer with lacquer thinner. If those don't soften the finish, then it's probably a phenolic or alkyd varnish which will require stripping.

Here is a good article on refinishing by Bob Flexner.

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You can test the finish by applying different types of solvent in an inconspicuous location on the piece of furniture. For example, you can remove Shellac with denatured alcohol. Bob Vila's website outlines a few common solvents that work for certain finishes in an article about removing varnish.

Some types of finish, like lacquer, burn into the existing layer when you apply a new coat. Other types of finish, like polyurethane, do not burn in, so if the topcoat is damaged you should ideally either uniformly sand through that coat across the entire piece, or you'll need to strip the finish all the way down to the wood and apply all-new finish.

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    Perhaps an explanation of "burn in", or use of different wording, would make this easier to understand for those unfamiliar with finish terminology. – Graphus supports Monica Apr 25 '15 at 4:56
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    When rob says 'burn in' he is referring to the fact that a new coat of lacquer actually partially dissolves/melts the existing lacquer surface and fuses with it. It is not necessary to sand the existing finish to create a surface that the new coat can bond to, only clean it well beforehand. – Ashlar Feb 19 '16 at 3:34
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You could test what kind of solvent will remove it. Shellac is removed with alcohol, lacquer with lacquer thinner, and varnish with paint thinner. Obviously do this on a part that is not visible if possible.

Perhaps a better way would be to just strip part of one piece, and try different finishes (stripping between) until you get the look you want, then use that process on the remaining pieces.

  • Just to note that dried varnishes tend to be soluble in something like paint thinner only initially. Because they are a reactive finish or conversion finish, once fully cured the finish has changed chemically and will be minimally soluble or completely insoluble in regular paint thinner and a stronger solvent would be required to dissolve them (e.g. as found in a dedicated paint stripper). – Graphus supports Monica Apr 25 '15 at 5:04

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