Is knotting the same stuff as sanding sealer?

sawyer

You know the stuff you paint on knots before you paint over them to stop them bleeding through?
 Is that the same stuff as sealer and can I use it as a sealer? 
Also , water based varnish. Can I use that as sealer and spray nitro over the top?
May be a stupid question, but I've got loads of both, so thought I'd ask before trying. Cheers

Simo

I always recommend making your own shellac from flakes, as it performs better than anything off the shelf, but yes.. Knotting is just Shellac mixed with alcohol, so it's the same ingredients as a shellac based sanding sealer and therefore should work fine. However, the quality may vary depending on the brand, so I'd suggest testing it on scrap first to make sure it dries/hardens fully.

You can apply any finish over the top of shellac, water or solvent based.

sawyer

Cheers fella

Corvus

Loads of things can be used as or called a sealer, any thinned lacquer or clearcoat, acrylic clear, shellac, whatever. Sanding sealers are generally different in having stearate added to fluff & bulk them up, so they can act as a sort of grainfiller and help sand well.

I use a sealer (either shellac or thinned clear/lacquer) before grainfilling, it helps some fillers not to sink as much plus helps show up anything missed in the sanding. But it's not really essential.

Waterbased clear; there's a chance product details/PDFs might talk about compatibility but likely not, with them being meant as final coats. With all the makes & materials out there I doubt it's possible to generalise about what might go over the top OK, but a test should sort it out. Also it'd be useful to see whether it shrinks back over a week or two, if other coats are going to go ontop.
Being water based there's a better chance of nitro/solvent not pickling it up, but if it was me I'd be doing a test to check it out.

sawyer

Thanks for information. Greatly appreciated