That’s why we’re all here, to learn from each other! Your post pointed me to a new use for shellac, so I learned something too. Pound cut is basically how many pounds of shellac flakes get dissolved in a gallon of denatured alcohol. If you use a lot of it, it’s cheaper to mix your own. Just mix as much as you need.
Also worth considering is that the seal coat (sanding sealer) is a dewaxed shellac where the clear or amber (finishes) are not so they can interfere with the adhesion of other finishes. You have more control when you mix your own but the premixed cans and spray cans are so convenient.
Shellac is the excretions of the Lac bug in India. That is harvested and is boiled and the dried into flakes. The picture posted is the waxed version. There is wax in the shellac flakes and when you mix it with aclohol and let it sit the wax floats to the top. You would remove the wax because the wax can cause film finishes to not stick to the surface of your project well and be spotty at best. Zinnser makes a dewaxed version that looks similar but is called Universal Sanding Sealer. This commercial version has had the wax removed. The Universal Sanding Sealer can be used with oil or water based top coats.
The pound cut is referencing how many pounds of shellac flakes are dissolved in a gallon of denatured aclohol. Shellac comes in different colors and those colors are determined on what the Lac bugs ate. The range of colors go from light to dark. You can buy the dried flakes of shellac and dissolve it in denatured aclohol but it is a messy process and you have to have a way to store the mixed shellac. Over time in storage the aclohol evaporates but can be replenished by simply adding aclohol. The trick is knowing how much aclohol had evaporated and how much to add. The Zinnser version is ready to use and like regular shellac dries very fast. However the aclohol fumes can be hazardous so use in a well ventilated area and stay away from flames and smoking during use.
Shellac is a traditional finish for furniture. However it is not very durable compared to modern film finishes like polyurethane. Shellac has been around for hundreds of years in the west and a lot longer in India as a traditional finish. Shellac gives some protection but for CNC use it helps stabilize the surface of your carving and helps to seal up carving when you are going to paint and helps keep the paint from being soaked up into the hollow straws that wood is made of.
So if you want to use shellac get the dewaxed version. The good thing about shellac is it can easily be sanded off. Almost all shellac gives wood a slightly yellow or warm appearance. Personally I like that effect. So if you dont want that effect test your shellac before applying it on a project. Shellac is good stuff but not for every situation.
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This is really great information. Thank you!
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