Shellac Cut Calculator
Weigh flakes for any cut, dilute between cuts, and see why a 5-pound cut is only 3.3 times the concentration of a 1-pound one.
Alcohol is taken at 0.789 g/mL, which is close enough for a shop. Dewaxed flakes and waxy flakes dissolve to slightly different volumes; the cut convention ignores that, and so does this. Nothing is uploaded.
A 5-pound cut is not five times a 1-pound cut
A cut is pounds of flakes per gallon of alcohol — a ratio to the solvent, not a share of the mixture. So as the flakes go up the alcohol stays where it is, and the proportion that is actually shellac climbs more slowly than the number suggests. A 1-pound cut is 13.2% solids by weight; a 5-pound cut is 43.2%. Five times the cut number, 3.27 times the concentration.
| Cut | Solids by weight | Against a 1-lb cut | Flakes per litre of alcohol |
|---|---|---|---|
| 0.5 lb | 7.06% | 0.54× (cut ratio 0.5×) | 60 g |
| 1 lb | 13.18% | 1.00× (cut ratio 1×) | 120 g |
| 1.5 lb | 18.55% | 1.41× (cut ratio 1.5×) | 180 g |
| 2 lb | 23.30% | 1.77× (cut ratio 2×) | 240 g |
| 3 lb | 31.30% | 2.37× (cut ratio 3×) | 359 g |
| 4 lb | 37.79% | 2.87× (cut ratio 4×) | 479 g |
| 5 lb | 43.16% | 3.27× (cut ratio 5×) | 599 g |
Which matters because film build follows the solids, not the label. Stepping from a 1-pound cut to a 2-pound one expecting twice the build gets about 1.77 times it. The gap widens as the cut climbs — and closes below a pound, where there is so little shellac relative to alcohol that the denominator barely moves and the relationship is very nearly linear after all.
Diluting is a ratio of cuts
The dissolved flakes do not change when you add alcohol, so the final volume has to be the starting volume times the ratio of the cuts. Going from 3-pound to 1-pound means ending up with three times the liquid — adding two volumes of alcohol, not one.
| From | To | Add per 1000 mL | You end up with |
|---|---|---|---|
| 3 lb | 1 lb | 2000 mL (2.00 volumes) | 3000 mL |
| 3 lb | 1.5 lb | 1000 mL (1.00 volumes) | 2000 mL |
| 2 lb | 1 lb | 1000 mL (1.00 volumes) | 2000 mL |
| 2 lb | 1.5 lb | 333 mL (0.33 volumes) | 1333 mL |
| 5 lb | 2 lb | 1500 mL (1.50 volumes) | 2500 mL |
Halving the cut does mean doubling the volume, so the instinct is right in that one case and wrong the moment the ratio is not two. There is also no diluting upward: adding alcohol can only ever lower a cut, and to raise one you dissolve more flakes into it.
How to use
- Enter the cut you want and how much alcohol you are using.
- Weigh out the flakes it gives you.
- Or enter a stock cut and a target to dilute instead.
- Read how much alcohol to add.
Frequently asked questions
What does a pound cut mean?
Pounds of shellac flakes dissolved in a gallon of alcohol. It is a ratio to the SOLVENT rather than a share of the mixture, which is where most of the confusion comes from — a 1-pound cut is 13.2% shellac by weight, not 1% of anything.
Is a 2-pound cut twice as strong as a 1-pound?
No, about 1.77 times. The flakes double but the alcohol stays where it was, so the denominator grows too. A 5-pound cut has five times the flakes and 3.3 times the concentration, and the gap widens the higher you go.
Why does that matter?
Because film build follows the solids, not the label. Stepping up a cut expecting proportionally more build gets less than that, and thinning down removes less than expected. It is a small effect at one or two pounds and a large one at four or five.
How do I dilute a heavier cut?
The dissolved flakes do not change, so the final volume is the starting volume times the ratio of the cuts. Three-pound down to one-pound means ending with three times the liquid — adding two volumes of alcohol, not one.
Is halving the cut the same as adding an equal volume?
Yes, in that one case — 2-pound to 1-pound does mean doubling the volume. The instinct is right there and wrong the moment the ratio is not two, which is why it is worth working out rather than assuming.
Can I make a cut stronger by adding alcohol?
No. Adding alcohol can only lower a cut. To raise one you dissolve more flakes into it, and the calculator will say so rather than producing a number.
What cut should I use?
Depends on the job, and thinner is usually more forgiving. A 1-pound cut wipes on easily and builds slowly; a 2-pound cut is a common brushing strength; heavier cuts set fast and are hard to work. Shellac redissolves into the coat below, so many thin coats behave better than few thick ones.
Does this send anything anywhere?
No. Every figure is computed in your browser, and nothing is uploaded or stored.
🔒 This tool runs entirely in your browser. Nothing you enter is uploaded, logged, or stored.