Official Luthiers Forum!

Here is the latest Luthier Tips du Jour video - The topic is how to apply the shellac based finish known as Royal Lac. This video as well as all my other videos are available via my website, http://www.obrienguitars.com/videos , LMI's website or on youtube.
Enjoy!

Thanks Robbie!
I may have to give this a try.

you are welcome. it is very easy to work with.

Thanks Robbie.
I'm guessing that if you don't use seal-lac you'll have problems.

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Not necessarily. I have tested it with and without and have seen no issues

Thanks for the info. Are there any particular woods where your experience would tell you seal-lac is a good idea? Or probably not needed?

Great video, by the way. As a beginner I find it very helpful to see you doing things. There are many things you could explain to an experienced woodworker in a few sentences, but to a beginner it just doesn't click until I see it.

I contacted Vijay, the manufacturer, to get his take on this and to offer an in depth answer to your question. Here is his response.

Royal-Lac can be used without Seal-Lac on any bare wood as you did with your sample boards. As a matter of fact that is what is done for the guitar top. Although some put a thin coat of shellac as a sealer.
Most finishes are many a times applied after the wood has been dyed or sealed with a pore filler. As would be for the back, sides and neck of a guitar. In this case it is always a good idea to use Seal-Lac or even dewaxed shellac as a sealer and a barrier coat. Two major reasons:
1) Since Seal-Lac or shellac is a thermoplastic polymer, its adhesive qualities are the best. Moreover when Royal-Lac is applied on top of it, it reactivates the shellac and melds with it to form a single layer. In this way we get excellent bonding as well as durability after cure.
2) The Seal-Lac or shellac also acts as a barrier if a amine based epoxy or glue (most are amine based) or pore filler is used. Any residual amine on the wood surface will reduce the acidity of Royal-Lac that may lead to failure in future.
So the bottom line is: Always apply a thin coat of Seal-Lac or shellac, level sand it and apply Royal-Lac. You will get a finish that will last you a long time.
One more area I would want to touch; It is not a good practice to apply a coat of Royal-Lac and then apply some sort of dye and top it again with Royal-Lac. Always, dye the wood first, apply layers of Seal-Lac or shellac and then start Royal-Lac application.
Finishing is a tricky business. Most finishes fail due to application or process errors. Creating the proper environment for the molecules to move and react with each other is paramount to a finish's success.
Regards,
Vijay