We make our own shellac varnish, using traditional recipes. We use only the freshest shellac flakes (fresh orange flakes, below), and use lab grade isopropyl alcohol as the carrier. We do not use methyl or ethyl alcohols because of the higher level of toxicity through fumes.
Typically, these shellac flakes are de-waxed, meaning a good portion of the inherent waxes have been removed so that when the shellac is dissolved into a viscous medium there will be almost no sediment left on the bottom, while also allowing the applied shellac to cure into a hard, clear and lustrous surface. A rule of thumb: the less wax, the harder the resin. The harder the resin, the more likely it will crack (alligator) over time through seasonal expansion/contraction of the coated object. Finding the happy medium between wax and freshness is the key to creating a lasting finish.
We make our brushing shellac varnish from 1/2 lb of fresh shellac flakes dissolved in 600ml isopropyl alcohol. We mix it in a clean quart canning jar. During the day, we shake it occasionally. We cut accreted gelatinous shellac flakes at the bottom of the jar using a clean serrated stainless steel knife once a day. We turn it over continually during the day as it dissolves, and the jelly like substance stretches itself into a suspended liquid resin as it dissolves. Within three days, we have brewed a completely viscous 3-lb cut shellac varnish. We decant into another fresh quart jar after it is thoroughly dissolved. Seems like overkill? Not in our experience.
From that quart jar we pour shellac into smaller jars for our brush use or for French Polishing. Then we cut to 1- or 2-lb shellac by adding additional lab-grade alcohol. Further, during a day of coating an object, we may add a small amount of the alcohol to keep the viscosity at the desired limit, as the alcohol evaporates when the jar is open.
RANDOM THOUGHTS AND NOTES REGARDING SHELLAC:
We have had failures using shellac flakes from large suppliers who sell to both the art markets and to large pharmaceutical houses, and tend to store their shellac flakes for years. After much research, we now have a source that is smaller and guarantees that his flakes are stored for a very short time. Further, his are processed in a manner which insures long-term viability of the varnish film. The difference in the shellac is amazing; stretch-ability and extended brushing time.
Lab grade alcohol usually must be purchased from a conservation or specialty store online; it is rarely found at the local hardware store.
Shellac flakes should be stored in a cool, dry, dark place.
Shellac flakes which do not dissolve are old.
Shellac flakes which are clumped are old (below.)
Shellac flakes stored more than one years and/or stored in a warm environment should be discarded or considered suspect. Mixed shellac over six months old should be discarded.
A thinner, more viscous cut can be created for French polishing or other applications by using less shellac flakes to the 600ml of lab-grade isopropyl alcohol.
Finally, beware commercial pre-mixed shellac, for it is not the shellac varnish found on a historic antique with its original shellac varnish intact. Shellac that is pre-mixed is invariably old, even in the best stores, and contains extenders and other chemical additives which are intended to replace or mitigate the losses of valuable waxes taken out during processing. These formulas are not traditional and often result in premature cracking and flaking of the varnish.
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