how to remove polyurethene from a clock, need help

Posted: Thu Feb 24, 2011 9:23 am     Post subject: how to remove polyurethene from a clock, need help

i recently won a rail road style cuckoo clock off ebay and i see that someone put shellac or polyurethene on the clock. What is the best and safest way to remove this from the clock to bring it back to original?

Posted: Thu Feb 24, 2011 2:29 pm     Post subject:

Two different types of finishes with two different products for removal. Shellac can typically be removed with denatured alcohol. Poly would more than likely require some type of stripper. Any options should be tested in an inconspicuous area to determine what finish is on the clock. Note that all solvents and strippers (to the best of my awareness) are dangerous to human health, so make certain to read any warnings/instructions included on the product canister. For removing old finish, you should also look into the appropriate safety equipement for yourself (dust masks, gloves, etc.). Make certain you are working in a well ventilated area when you proceed.

As a side note: Removing the original finish is quite the task, so I would recommend some homework prior to any experiementation. There are several books out there, written by experts, that provide tips and suggestions on refinishing a wood piece. Authors to note: Bob Flexner, Michael Dresdner, and Jeff Jewitt. Local furniture restorers may also have some helpful advice to pass along. Note that you will need to re-coat the clock with a finish of your preference, to help protect the wood of the case for years to come, once all the old finish has been removed.

Posted: Fri Feb 25, 2011 4:26 am     Post subject:

the reason i want to remove this finish is i don't think it's original. What's the common finish for a clock of this age. probably early 1900's?

Posted: Fri Feb 25, 2011 4:53 am     Post subject:

shellac would be the finish for the 1900's. denatured alcohol will remove the finish. You may be able to use a straight edge razor blade to remove the finish w/o chemicals by lightly scraping the surface.

Posted: Fri Feb 25, 2011 3:02 pm     Post subject:

Polys and varnish are going to be way more durable than shellac, which is one of the primary reasons shellac has declined as a finish coating over the last half of the 20th century (with the exception of French Polishing and pre-finish sealer or washcoat coatings).

The problem with shellac is that it has a poor resistance to water, alcohol, heat, and alkalis (which includes lye, ammonia, borax, and soaps with phosphates). Don't accidentally spray the finished shellac surface with glass cleaner when cleaning any glass portions of the clock (if applicable).

The drawbacks admitted, shellac does have its advantages as well. For example: It is probably the least hazardous of all finishes to use, and one of the only finishes that the FDA has approved as "edible" (although I would not recommend eating any). Also, while shellac provides a weak barrier against water penetration, it is an excellent barrier to impede the passage of water vapor exchange. In other words... It can withstand periods of naturally humid conditions despite that it can not impede direct water penetration. It is for this reason that it is regarded as a great sealer or washcoat prior to final finish application of a varnish or ploy.

Posted: Thu Mar 03, 2011 8:30 am     Post subject:

how can i tell what is exactly on my clock. it's very shiny. would it be Varnish? i mean who ever had this thing put it on the numbers and everything. Not sure what they were exactly trying to accomplish.

Posted: Thu Mar 03, 2011 2:45 pm     Post subject:

The "shiney-ness" is probably due to the sheen of the finish (whether a satin, semi-gloss, or gloss sheen). According to Michael Dresdner (finishing advice columnist for various woodworking magazines), most strippers will remove most finishes. If you do not know what kind of finish is on the clock assembly, select a "paint & varnish remover" type stripper.

Shellac and laquer would be the only exceptions that would not necessarily be removed by a stripper. Before using a stripper, you may want to test, in an inconspicuous area of the assembly, to see if your existing finish is either lacquer or shellac. You can test using either product's solvent (denatured alcohol for shellac; laquer thinner for lacquer). If niether solvent seems to thin/remove the finish, then you can move on to a stripper.

Generally, the more hazerdous a stripper is, the more quickly it will work. The safer the stripper, the longer it will need to be left applied to the surface. All said and done, I highly recommend further research (reading) in regard to the subject. If possible, inquire with furniture restorers in your area for more professional advise. Stripping/refinishing can be a beastly project, and it would be best to have as much knowledge as you can about the subject.

Posted: Tue Jan 31, 2012 10:55 am     Post subject: Finish for a clock from 1700-1730

Hi
Interesting post. I also have the same issue for my oak clock. I am curious as to what would the original finish have been from that era? I intend to remove the poly finish with chemical stripper and then reinstate whatever the original finish would have been. Any advice would be appreciated....

Posted: Tue Jan 31, 2012 1:44 pm     Post subject:

If the clock can be dated between the 1700-1730's, then it more than likely has shellac on it. Try using shellac's solvent (denatured alcohol) in an inconspicuous area to see if it removes the finish.