Hello,
My name is Shown , from Malaysia and I am new to this forum. I do woodworking as a hobby. When I restore old furniture I have a problem with choosing a finish that will be compatible with the underlying existing one ( If I decide not to sand it down to bare wood) . Is there a way to find out what the old finish is? Or how to find out whether the one that I intend to use would be compatible with the old one? I stay in a rural area and the shops stock mainly polyurethane based finishes.
Then also I am confused when the labels on the finish state that for thinning purposes one can use .. mineral spirit, white spirit, turpentine, thinner. Are all these 4 items the same, interchangeable? There has been times when after dilution with one or the other, the surface to be painted becomes ‘bubbly or flaky’ when the diluted finish is applied, thus ruining the piece of work.
Thank you for any suggestions!
Replies
You can test your finishes easily, if you can get the solvents needed. You will need a little of each of the following:
...and a few Q-Tips or small, tiny pieces of cloth.
Wet the Q-Tip with some denatured alcohol, and rub a spot of finish with it. If the finish dissolves (makes the swab gunky) then it is shellac.
If that doesn't happen, do the same with lacquer thinner (in a different spot). If you succeed, the finish is lacquer.
Anything else (varnish) would come off with the methylene chloride, with the possible exception of old-fashioned Milk Paint. That stuff is tuffer than nails and a pretty desirable finish on a true antique.
I generally clean whatever I'm about to tackle with mineral spirits first to get off dirt and any wax that's been applied.
I'm not well-versed in the differences between the various names you cited for the various thinners, but "pure gum turpentine" is what I use most of the time. The mineral spirits and thinners may functionally be equivalent to each other, but hopefully we'll get "someone who knows" to comment!
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
Shown,
Welcome. I'd recommend that you purchase of copy of Bob Flexner's "Understanding Wood Finishing". It's laoded to the hilt with real world useful information and guaranteed to be worth the price many times over in what it will save you in frustration and redos.
Dear GH, FG
Thank you for the prompt replies and help. I am thrilled to know that there are so many helpful and knowledgeable souls out there! Will try as suggested, including getting the book.
Shown
Mineral Spirit = White Spirit.
They are both inorganic forms of Turpentine and serve the same purpose but are generally cheaper.
IanDG
>>They are both inorganic forms of Turpentine
Just a nit really but turpentine comes from pine trees and mineral spirits, white spirits, paint thinner and naphtha are all petroleum products.
They all can be used to thin oil based finishes but each will impart some slightly different performance characteristics to the finish.
>>They are both inorganic forms of Turpentine
Just a nit really but turpentine comes from pine trees and mineral spirits, white spirits, paint thinner and naphtha are all petroleum products.Inorganic
1 a (1) : being or composed of matter other than plant or animal : MINERAL (2) : forming or belonging to the inanimate world b : of, relating to, or dealt with by a branch of chemistry concerned with substances not usually classed as organicWhite spirit or Mineral Spirit -- the terms are synonomous -- was originally called Turpentine Substitute and now has almost totally replaced the use of Turpentine.IanDG
My issue was not with "inorganic" but with implying that petroleum based products are "forms of turpentine." Turpentine is a totally different product but can be called a "paint thinner".
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