Shellac precipitate

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    Roberto Fischer

    I have a can of bullseye Shellac (USA bought), which is pretty thick premixed shellac solution. I realized that leaving the can contents on a jar causes some precipitate to decant over time, leaving me with the amber solution on top and this precipitate at the bottom. If I shake to mix, the whole liquid becomes cloudy.

    I’m wondering what this is and whether I should really only use the amber solution part.

    I remember Sven-Olof Jansson commenting about filtering his shellac solutions and I’m not sure if this is related.

    The photo attached is after about 24 hours of decanting. Before I picked it up, the precipitate was concentrated at a much thinner layer at the bottom. I’m not sure how long it takes for it to completely settle down.

    Sven-Olof Jansson

    My understanding is that Bulls Eye Shellac is a waxed version, and thus the precipitate is the wax. The dewaxed one, the company labels Seal.

    The attached link shows a French brand of wax containing shellac (marketed in Sweden). There is definitely a lot of cloudiness at the bottom.

    This far I’ve filtered/strained dewaxed shellac (100 µm). It did remove a lot of small particles, resulting in the disappearance of the knottiness from the surfaces. According to what I’ve read, decanting is the method for getting rid of the wax; or one can simply use the top layer. Straining/filtering waxed shellac requires the wax to first be dissolved (emulsify is possibly more correct), which it seems to do readily enough. According to Jeff Jewitt’s book “Taunton’s Complete Illustrated Guide to Finishing (ISBN-13: 978-1-56158-592-2) all finishes should be strained. Presumably that includes wax containing shellacs.

    Blond waxed or dewaxed shellac made no difference to my eye when they were applied side by side on the bottom of an oak box.

    Sven-Olof Jansson
    London, UK; Boston, MA

    Roberto Fischer

    Good information, thank you.

    From what I’ve read before, is waxed shellac fine as the only type of finish but not fine as a primer for another water borne finish? Are there other differences? For french polish, which ones is more appropriate?

    Sven-Olof Jansson

    Always happy if I can be of assistance.

    Jeff Jewitt appears to stick to dewaxed all the way; partly because of what you mention (thanks, was only aware of that polyurethane varnish doesn’t go with waxed shellac), and partly for no mentioned reason.

    Tom Fidgen has produced videos on French Polishing. I believe he too uses dewaxed shellac. He also has the virtue of not mystifying the technique.

    Prof. Johan Knutsson has written a very interesting book on “The Craftsman’s Alternatives” (sadly not in English). He details on the use of lac (the resin behind shellac) and its use during the 18th century by the specific Lacquer Guild. It is perhaps noteworthy that shellac in French is gomme laque.

    Derek Jones mentions in his book “French Polishing” (ISBN 978 1 86108 711 9) that dewaxing was invented in 1830, though he does not state anything on what type of shellac to use.

    Richard Bitmead, in his 1910 book “French Polishing and Enamelling” (Project Gutenberg) gives two pieces of information: French polishing had been use in France before the technique became popular in [Victorian] Britain; and that the shellac should be dissolved in very concentrated alcohol. The latter, I think, was achieved by filtering through active coal, a process discovered in France during the 1790s.

    Then R. Bitmead eventually gives the final clue: Waxed shellac was prone to impart discolouring of light coloured woods, as to why the Society of Arts in 1827 offered a gold medal or 30 guineas for a polish deprived of the colouring matter.

    All in all of the above: Dewaxed shellac is to be preferred.

    Sven-Olof Jansson
    London, UK; Boston, MA

    Larry Geib

    There is method for dewaxing I got from FWW magazine . It works with Bullseye or flakes.
    Mix about 3/4 waxed shellac and 1/4 mineral spirits in a condiment bottle or old glue bottle. Seal the spout. Shake Vigorously for a minute or two. The spirits will dissolve the wax and absorb it.

    Put the bottle upside down for 24 hours and the spirits/wax will rise or the top and the shellac/alcohol will be on the bottom towards the spout. Just squeeze off the shellac. Stop when the oily layer gets to the spout area.
    Alternatively, you can use a turkey baster to carefully reach down into the mix and suck out the bottom layer of shellac, neither method is 100% efficient, but you can get close.the condiment bottle method works better if you don’t fill it more than about 2/3 so you can squeeze more efficiently.

    The waxy mineral spirits can be used for other things. It is supposedly good for a lubricant for French Polish ( I haven’t done that) or it can be added to beeswax if you are making soft wax.

    • This reply was modified 1 year, 3 months ago by Larry Geib.
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