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
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
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 ...