I am trying to achieve a glossy finish on a piece of open grained wood, so I am looking at applying grain/pore filler to even out the surface. The articles/videos I've found online pretty much all say to seal the wood with shellac or similar prior to applying grain filler.

What is the primary advantage of using sealer prior to applying grain filler? Am I asking for trouble if I apply grain filler without applying sealer?


What is the primary advantage of using sealer prior to applying grain filler?

The main reason to seal1 is arguably to minimise the over-absorption of the binder in the filler, which can lead to chalking and/or adhesion problems down the line. This isn't an issue with all fillers, but it certainly can be with traditional oil-based pore fillers for example.

Other sources state that it's to prevent the filler penetrating the broad areas of the wood, making it look murky or grubby, and there's certainly something to that with certain fillers. Still others claim it's to improve adhesion (dubious).

Regardless of the underlying reason, shellac2 is excellent for this as it dries so quickly and reliably, even in a cold workshop.

Am I asking for trouble if I apply grain filler without applying sealer?

It depends on the filler type. With certain caveats you should be guided by the instructions that come with the filler or are listed on the manufacturer's website.

Personally I would tend to err on the side of caution here and suggest you just do it anyway. It's not like it adds a lot of extra time if you're using shellac — shellac coats can be considered dry in 15 minutes or less.

Because of your stated aim in doing this just to note, grain filling is not necessary to achieving a glossy finish. What it does is give you an uninterrupted shine, where the pore structure of the wood is hidden and you get a reflective surface akin to a sheet of glass. But there's no actual difference in gloss level per se.

And some people prefer to let open-grained woods like oak, ash and sapele exhibit their natural grain structure at least to some degree. If you want a partially grain filled appearance it's often enough to just build up a good few layers of your film finish, e.g. at least four or five full-strength coats of poly, and this will occur without any additional effort being needed. It's harder to get the same level of filling of the grain with shellac or lacquer without some sanding back, due to how thin these generally go on (and they shrink back as they dry due to the loss of the solvent).

1 Be aware you're not actually sealing the wood; even two wet layers of 2lb-cut shellac applied by brush will only partially seal the surface of wood, and you generally apply much less than this prior to grain filling.

2 Note that it is not necessary to use dewaxed shellac for this purpose; traditionally such 'sealing' was done with plain ol' waxy shellac because dewaxed versions simply weren't available.... and obviously it didn't cause a problem.

  • This is a fantastic answer, thanks! I am trying to retain as much of the natural wood appearance as possible, so I am only finishing with wax, or oil and wax, after sanding to a high polish. On one of my test pieces, I applied wax with no other finish, but some of the wax packed into the pores and left ugly white spots. On another, I applied clear-drying filler (without sealer) and then wax, and it looks great. I'll get some shellac and see how it compares using it as a sealer. Apr 13 at 16:13
  • Ah, if you're intending to wax then it's also a good idea to use sealer beforehand anyway. Although you can build up a perfectly good shine with wax alone (you just keep going until you get a shine) it's much faster if you 'seal' the surface first, and again shellac is excellent for this. Re. the wax in the pores, I know what you mean! Two ways around this are to either A) use coloured wax that isn't noticeable if left behind B) use a stiff brush to remove the wax from the pores. A few pros use brushes to apply and buff wax partly to avoid this issue. BTW bravo for doing test pieces!!
    – Graphus
    Apr 14 at 8:04
  • BTW if you oil first you'll get a significantly deeper tone, and it may exaggerate any yellow/orange colouring (depending on the natural colour of the wood naturally). I have to also mention though, wax is not a good finish for utility items; it's really only suitable for decorative items like turnings or decorative boxes, and in furniture bookshelves or other things that aren't moved or handled much.
    – Graphus
    Apr 14 at 8:05
  • Re. getting shellac, it's super handy to have some on hand for a woodworker because it has a number of uses beyond being a finish in its own right. In case you haven't read this elsewhere it's considered best to mix your own, and it's very simple and straightforward to do this if you buy it in flake form. The dry shellac will keep truly indefinitely if protected from light (brown glass jar, or inside a cupboard or drawer) and air. Once mixed the guidelines say it'll only last about six months, while commercial liquid shellacs will generally last longer they do still have a finite shelf life.
    – Graphus
    Apr 14 at 8:10
  • At this point, I’m mostly experimenting. I do have a project in mind, and the pieces for that will be mostly decorative, with occasional gentle use. The grain filler I have worked fine on unsealed wood (no chalking or fogging), but I got much better results on hickory than on walnut. I’m trying different techniques, because IMO oil and oil-based finishes reduce the contrast of some woods. So I’m trying to come up with something that gets me a nice gloss, without the plasticky feel of polyurethane, and without the deepening/darkening of oil. Apr 23 at 19:34

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.