Saturday, November 5, 2011

Making Aqueous Shellac


Water-based shellac? You mean you can get shellac, which is soluble in alcohol, to dissolve in water and be used the same way? That’s right.

WAIT… IS THIS “MAGIC”?


Before I walk through the process, let me give a quick insight into why this “magic” works: The key here is to understand molecular polarity. It is helpful to think of polarity as a line with one end of the spectrum being polar and the opposite being non-polar. All materials fall somewhere on the line of polarity. For a material to dissolve, it must be introduced to a solvent of the same polarity. Water is very polar and petroleum products are non-polar. Hence, oil and water don’t mix. A solid that is non-polar will dissolve in non-polar solvents, like mineral spirits. A solid that is polar will dissolve in polar solvents, like water.

So, if the shellac resin is soluble in alcohol, how then can we get it to dissolve into water (which is slightly more polar than alcohol)? Answer: Change the ph of the water.

By adding a small amount of Sodium Tetraborate (commercially sold as “Borax”) to the water you cause it’s polarity to shift toward that of alcohol. Get the proportion right, and the shellac begins to dissolve.

This slightly over-simplified explanation is useful enough for our workbench experiment.

THE EXPERIMENT


A dear friend of mine, Craig Cianciolo, Wood Finishing Specialist at U.S. House of Representatives, shared the recipe he developed from reading Robert D. Mussey and Edward Hicks. He has given me permission to share my experiment here on The Diary.



Aqueous shellac, or Water-borne / water-based Shellac, begins with a list of ingredients and supplies:

A hot plate or stovetop
A small sauce pan
A glass jar (with lid)
Fine Mesh Paint Filter
Distilled Water
Borax 20 Mule Team
Dewaxed Shellac Flakes

The process begins by putting 12 parts (by volume) distilled water into the jar. The jar (with lid on) is placed into the saucepan and water is filled to the water level in the jar. (Make sure you place it onto a dishcloth or such so that the glass isn’t touching the bottom of the pan.)



Heat your 12 parts water up to just below boiling (170-190 degrees or so). Remove the jar from the pan and add 1 part Borax into the water, stirring until fully dissolved.



Once dissolved, the ph of the water has shifted. You can now dissolve your shellac. Take 2 parts dewaxed shellac flakes and pour them a little at a time into the jar, stirring frequently. The shellac, as always, will take a little while to dissolve. It took me a few hours for this to dissolve completely. Coming back over the next few hours to give the jar another stirring definitely helps the process.



When cooled down, and strained through a fine mesh filter, this finish can be applied like solvent shellac. Other than a longer dry time it seems to perform very similarly in all other ways.

I personally found this formula a little light and desired a “heavier cut” of shellac. After experimenting, I reheated the finish in the saucepan, and dissolved 2 additional parts shellac into the solution. It worked like a charm.



THE FINAL RECIPE


My final aqueous shellac recipe, measured by volume:

12 parts distilled water
1 part Borax 12 Mule Team
4 parts dewaxed shellac flakes

So with this recipe you can make your own homemade aqueous shellac. Using it is a bit surreal, I must admit. The harshness of the alcohol smell has been so closely associated with shellac in my mind and the aqueous version just smells kinda… well… fruity. It’s quite pleasant really. I recommend you give it a shot. I think it may be worth your time experimenting.



Further Reading on Solubility:

Chris Stavroudis and Sharon Blank, Solvents & Sensibility, WAAC Newsletter, Volume 11, Number 2, May 1989, pp.2-10

Rivers and Umney, Conservation of Furniture, Butterworth-Heinemann, 2003, pp.515-526

4 comments:

  1. Thank you Joshua for sharing this formula/experiment for water-bourne shellac. Also, please thank you friend Craig researching the process. I look forward to trying this.

    How much longer did it take for the shellac to dry? One aspe ct of shellac finishes I've alway loved is the fast drying time.

    Thanks again,
    Ron Jones

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  2. Hey. You're welcome, Ron. Glad you were helped by it. It took maybe two to three times as long to dry. With solvent shellac, I push it sometimes pretty close between coats (especially if it's a small repair.) Evaporative coatings like shellac are a little less critical to become paranoid about timing. All that to say... my little test piece was left to dry for about 30 - 40 minutes between applications. A good test is if it powders up when sanded, you're good to go.

    Be well and have fun!

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  3. I just came across this, other than the odor and longer drying time, what are the advantages to this finish? How does it compare/hold up to regular shellac? Very interesting proposition. Thanks for info.
    Mark Behrens
    Pockets Full of Sawdust
    sawdustlife@gmail.com

    ReplyDelete
  4. Mark,
    I am not aware of any differences in performance once cured. This should certainly be tested! One other benefit to my situation is that I once I needed to overcoat a painted chest of drawers with a coating of differing solubility. Alcohol was too close but the aqueous version of shellac seemed a little more merciful to the underlying surface. (See: http://kleinrestoration.com/Paintedpineset.html ) Thanks for reading! Be well...

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