Can someone remind me of the formula?

[Dave Bagwill]

I have a 2 lb cut, I want to thin it to a 1lb cut, but I don't think it is just a matter of cutting the 2 lb cut in half. Am I right?

[John Link]

Equal parts 2 pound cut and ethanol will do the trick, if you want 1 pound cut.

[Dave Bagwill]

I think that would yield a 1 1/2 lb cut, but I cannot remember why I think that. Will check it out.

[Dave Bagwill]

Found a little chart. To me, it's counter-intuitive.

[John Link]

It might make sense if I knew more about how shellac dissolves. But I don't. Here is Shellac Finishes statement on mixing dry flakes, going from lower cuts to higher. Each step adds flakes to the same amount of solvent in direct proportion to the desired pound cut. Apparently, for V J, one fluid ounce of his material also weighs one ounce:

The so called ‘cut’ of shellac is best described as the ratio of shellac flakes in relation to denatured alcohol. A 1lb ‘cut’, means 1lb of shellac flakes dissolved in 1 gallon of denatured alcohol. However this is a large quantity for most woodworking shops. Moreover most shops do not own a weighing scale either. Hence a smaller amount can be mixed for a 1lb cut by taking 1oz. of shellac flakes and dissolving it in 1 cup of denatured alcohol. If a 2lb cut is required, simply increase the weight of the shellac flakes to 2oz. For a 3lb cut increase the weight to 3oz and so on for heavier cuts. Since a cup holds 8 oz, divide the cup into eight equal parts for measuring 1 oz. now you don’t need a weighing scale, only a cup from your kitchen.

[John Parchem]

I do what John does when cutting, but I really only want about a 1 lb cut. If you add an equal amount alcohol to a 2 lb cut it is a bit less than a 1 lb cut because the 2 lb cut has alcohol plus shellac. So a pint of a 2 lb cut does not have a pint of alcohol. I do not know what the formula is. It would be easy to calculate by taking a cup of alcohol, dissolving 2 oz of shellac in it and then measuring the volume of the 2 lb cut.

You can use the ratio of alcohol to finished volume to do the rest of the calculations. I do not do any of that. If a have a cup of 2 lb shellac, I add about a cup of alcohol to make a 1 lb cut.

[Dave Bagwill]

Thanks to you both, that's all I needed!