There has been alot of conversation as to how to cut a certain lb cut shellac to sume other cut. This was taken from Fine Woodworking and I hope that the table shows up corrctly but should it not refer to link:
Shellac Conversion Ratios
To convert remixed shellac to a dilute cut, add the appropriate amount of alcohol, as shown in the chart. For example, to convert a 2-lb. cut to a 1-lb. cut, add 2/3 of 1 part alcohol to a 1 part existing 2-lb.-cut shellac solution.
Parts Alcohol: Parts Existing Cut
Cut 1/4 lb. 1/2 lb. 1 lb. 1-1/2 lb. 2 lb. 3 lb.
1/2 lb. 1:1
1 lb. 3:1 7/8:1
1-1/2 lb. 4-1/2:1 1-2/3:1 1/3:1
2 lb. 5:1 2:1 2/3:1 1/4:1
3 lb. 8-3/4:1 3-3/4:1 1-1/2:1 3/4:1 1/3:1
4 lb. 11:1 5:1 2:1 1-1/4:1 3/4:1 1/4:1
5 lb. 12-3/4:1 5-3/4:1 2-3/4:1 1-1/2:1 1:1 7/8:1
(Update: Several readers have questioned the proportions in the chart. The numbers are correct, however, and here’s why: The mathematics for shellac dilution do not follow a general ratio formula because you are working with the weight of a substance in a volume. For example, say you want to take a 2-lb. cut down to a 1-lb. cut. It would seem logical that it would be a one-to-one reduction of shellac to alcohol, but it’s not. When you dissolve 2 lb. of shellac in 1 gal. of alcohol, you displace the original volume by 20 percent, thus giving you 1.2 gal. total in which 2 lb. of shellac are dissolved. So a 1-gal. volume of a 2-lb. cut shellac contains only 1.66 lb. of shellac. Three lb. in alcohol gives roughly 1.3 gal; 4 lb., 1.4 gal, and so on.)
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