As others have noted, shellac is a "hot" finish - each new layer dissolves the surface of the previous layer, as opposed to poly where each new coat merely sits on top of the previous layer. Sanding between layers of poly provides a mechanical connection between the layers.
On my current project I'm shellacing parts prior to assembly, being careful to avoid areas that will be glued or sanding those areas to bare wood later.
Got carried away on a pull out shelf - probably applied 15+ brushed on coats of one pound cut shellac in 30 -45 minute increments. The garnet shellac made the cherry ply shelf appear golden without obscuring the grain. Liked that look so did the same on the sides and top of a pull out box that will hold Scary Sharp plates. The finish looked glorious!
Let the box sit for a couple of days in a 60-75 degree shop while doing other parts and dry fitting things. When all the parts were ready and the whole thing had been dry fit just to make sure I hadn't miscut something, I set up the clamps, glued things together and clamped them snug but not tight.
Four hours later I removed the clamps - mainly Bessy K-bodies. Everywhere the clamp faces contacted the finish I got jaw imprints - not deep but noticable on the nearly glass smooth finish.
So the question is - To get a nice hard shellac finish
- how long between coats with a 1 lb cut?
- how long after final coat before the finish is hard enough to clamp without imprinting the clamp jaws into the finish (assuming 60-75 degree shop with 75-80% RH?
I really like the range of looks you can get with shellac Thin coats are quick and easy to apply, it loses its tack quickly so dust is less of a problem and the finish builds fairly quickly. . I also like prefinishing parts so the finish can be applied with the parts laying down flat.
But if I want a thick, deep prefinish and have to wait a week or so before clamping ...
charlie b