Reversible vs. Non-Reversible Finishing
by Alan Noel
Professional Wood Finisher
When I first started my shop some thirty plus years ago, I realized in short order the need to understand which finishing materials would work together and which would not. A good friend and mentor at the time was very kind in that he freely shared his knowledge with me, even though I was his competition. The following tips should help to clear the air:
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There are two basic types of finishing systems, reversible and non-reversible.
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Reversible finishes are LACQUER and SHELLAC. OIL-based and WATER-based finishes are non-reversible.
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Lacquer finishes are basically "finger nail polish." Each successive coat melts into the previous coat thereby creating one "homogeneous" coat when dry.
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Shellac works exactly the same way as lacquer. Each coat melts into the previous coat creating a homogeneous finish.
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All oil based finishes or ANY finish that is thinned with "mineral sprits," are non-reversible. This means that each coat will not melt into the previous coat.
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Water based finishes are the same as oil based in that they are non-reversible.
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To make all of these finishing systems work together simply sand the finish to be recoated with 320 or 400 grit sand paper. This will create fine scratches or "ruts" for the next coat to cling to.
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Be sure to sand all areas and remove the sanding dust with a tack cloth before re-coating.
This is a very simplistic explanation but one that will always work without getting into the chemistry of these materials.
As always, practice on scraps first.
Visiting Atlanta? Attend one of Alan's upcoming highly informative Highland Woodworking wood
finishing seminars:
January 15, 2014
French Polish Workshop
Visit Highland Woodworking's Online
Wood Finishing Supplies Department
Alan can be reached directly via email c/o Alan Noel Furniture Refinishing at
anoelfurniturere@bellsouth.net
.
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