Recommended finish to preserve older marquetry artwork

Question

I can be convinced that this is a duplicate of this other Q&A, but there isn't much there that seems to pertain to preservation of already well-dried wood art pieces. But I'll go along with what the community decides.

We recently were given a few small pieces of marquetry artwork that are a decade or so old at this point. These are not fine art pieces, but rather examples of Indian handcrafts purchased in that country as souvenirs.

(I do apologize for not posting photos, but I forgot to capture examples before I left home today. I will update this question with examples if it will help.)

Over the years, the North American climate has caused some of the pieces of marquetry to split, though the glue has held up surprisingly well. I'm told they have lost some contrast over the years, as well.

From our perspective, the aging just adds to their charm, so no one wants to treat these like museum pieces. In the interest of preserving these as-is, what finish recommendations for maintaining wood health (e.g., discouraging anything that might want to treat the artwork as a food source, minimizing further checking) would people have?

The existing "finish" is unknown, if it was finished at all. The surfaces are very matte, with a fair amount of gaps between the pieces that show no varnish or poly style finishes. It might have been oiled at some point by the original craftsperson.

I was thinking of just treating these like a cutting board or a spoon; some sort of stable mineral oil and/or beeswax (for no other reason other than that is what I have handy). I've also been reading about proprietary wood preservers and the old stand-by of PEG as a first or only step; but these pieces are not at all green, which is what most discussion assumes.

But I'm open to suggestion for any minimal finish that just keeps things as-is.

• We don't care if the finish is darkened; this will actually add to the look, as the original intention was to combine light and dark wood for effect. So a finish that increases contrast is ok.

• Something that is shiny or an "obvious" finish is less desirable, as the original look is rather raw and hand-made.

Full disclosure: I mention pests. There are unconfirmed reports that some sort of insect had to be cleaned off of these pieces after they were in storage (perhaps someplace in the South-East US, but this is a guess). There are no obvious pests on them now, and no obvious pest damage, but if that is a consideration there you have it.

I would also accept "leave it alone; it's been fine for decades so why mess with it". And given that I will probably not want to touch this with anything other than a soft cloth (i.e., no sanding between coats!) this is a totally reasonable answer. But we may as well harness the power of the Stack to see.

Answer 1

There are so many options you could use here — you could in essence use nearly anything — and at the end of the day anything you pick is going to be a compromise of some sort.

A natural oil will maximise contrast (see Most durable foodsafe finish to highlight chatoyancy from just a short while ago) but excess needs to be scrupulously removed, especially from recessed corners, to avoid gummy/sticky residue and the wiping/brushing needed to do this might pose a risk of dislodging pieces. In addition straight oils don't discourage insect or fungal attack¹.

I would personally be inclined towards using a film finish, applied very thinly so as not to build a film. Any very thin or dilute finishes give the look of finished wood without any obvious surface film and dilute wiping varnish or shellac applied similarly thinly (i.e. a "washcoat" or "spit coat") are two good choices here. As these are hard materials when they impregnate the surface wood fibres they harden the surface and improve dust resistance better than straight oils do. Wiping varnish, being an oil-based finish, will enhance the grain although not quite to the degree of a straight oil.

Waxing is something to consider. I wouldn't normally suggest wax as I'm against using it alone as a finish because it provides so little protection but it's fine for decorative pieces and items that see little or no handling. Applying the wax and buffing to a sheen may again pose a risk of disturbing pieces but both processes can be done carefully with soft brushes (think shining shoes) so little pressure is applied directly to the surface². Waxes are inert and won't promote insect attack, although I don't believe they'll do much or anything to deter it either.

As you say yourself though, doing nothing at all to them is actually a viable option, as it is with lots of things. Here their slightly worn, aged look could be seen as a large part of their charm..... even if it isn't how they looked when new, q.v. most present-day antique appreciation!

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¹ Although this can be improved with borax or other additives which may or may not be available, see here for a little on that.

² If you're keen on trying this I would buy a commercial paste wax or make your own (brief instructions given at the end of this Answer) then scoop out a spoonful and thin it to the consistency of softened butter or mayo that can be applied by gentle brushing. This will also mean a very small amount of wax is applied to the surface, which will be easiest to buff to a sheen. I do something similar to this when waxing old hand planes rather than using paste wax 'at full strength' so to speak.