"Gritty" shellac when sanding level?

[Tavy]

I wonder if this is normal, or if I'm doing something wrong, or something else?

When sanding the finish level on my latest restoration project I'm getting very gritty sanding dust that frequently clogs up the sandpaper. It doesn't seem to effect the final finish at all as long as your really careful, it's just really annoying and makes it harder work and less pleasant than it should be :disbelief: Back when I used ready-mixed shellac it was actually a lot easier to sand level (producing very fine dust that didn't clog anything much), albeit giving a much less effective final final finish. The sanding on this one gets harder the finer the grit, and even with OOOO wire wool the sanding dust is still coming up "gritty".

For the record I'm mixing (and filtering) my own shellac + about 20% gum sandarac, and the finish has had about 10 days to harden since the final body coat went on.

Cheers, John.

[Greg Mirken]

I don't know if this is related to your problem, but I use 10% by weight of gum sandarac to the amount of shellac flakes in my mix. Maybe the higher % of the softer gum is causing your clogging problem.

[Michael Lewis]

Also, how fresh is your alcohol? It picks up moisture from the atmosphere if allowed. I think this is one of the reasons "old" shellac takes longer to dry/cure than fresh does. Completely dry finish will powder when sanded.

[Tavy]

Also, how fresh is your alcohol? It picks up moisture from the atmosphere if allowed. I think this is one of the reasons "old" shellac takes longer to dry/cure than fresh does. Completely dry finish will powder when sanded.

The alcohol is from a fresh bottle, so I don't think that's the issue here.


I don't know if this is related to your problem, but I use 10% by weight of gum sandarac to the amount of shellac flakes in my mix. Maybe the higher % of the softer gum is causing your clogging problem.

I did wonder about that... strange thing is the finish actually seems to be as hard as nails, it's just that the sanding dust likes to roll up into little beeds that clog the paper and scratch the finish if you don't catch 'em quick.

Oh well... I've started so I'll have to finish now I guess... next time I'll try less Sandarac and see if that's the cause.

Thanks, John.

[Rick Turner]

That's a lot of sandarac compared to most formulas I've seen. And you may just not be waiting long enough for the shellac to dry. When it's all correct, shellac sands beautifully.