Re-purposing a Box—Part 3, Exterior Finish

After our initial assessment and de-construction, the next step in our process is to look after the exterior finish. In the case of this box, the finish is in quite good condition, so our efforts will be minimal.

1. The Original Finish

In our last post, we talked a little about how to use intact interior finish as a means of determining the appearance and nature of the original finish. The interior tray of this box is in almost perfect condition. This means that we don’t have to speculate as to how to duplicate it; we can simply use the tray’s finish as our model.

An alcohol swabbing proves that shellac is the original finish.

It has been well-established that shellac was used almost exclusively in finishing wood around the turn of the 20th century, and this box is no exception. To confirm this, we moisten a bit of cloth with 99% rubbing alcohol, and gently wipe the finish. If it softens, then leaves residue on the cloth (not just dirt, mind), then it is shellac. And our hypothesis is confirmed.

Shellac is an entirely biological product. The resinous secretions of a small Indian bug are pulverized, dissolved in alcohol, and clarified. The resulting finish is strong, water-resistant, and long-lasting. It is also beautiful: warm in colour, and capable of taking on a high shine (french polish—that glassy polish used on the best 18th century furniture—is just thin layers of shellac, each of which has been highly polished.)

Underneath the shellac is colour. Oak, the wood used in this box, was often darkend by exposing it to strong ammonia fumes. This results in the strong colour contrast in the figure of the wood. The colour is not deep, so if we want to preserve the original colour (which we do), we need to be careful not to remove it.

The original, damaged, finish

While shellac is a truly superior finish, there are a few effects which can take their toll. Sunlight is the worst, and most common. This box shows some damage to the shellac: some surface checking, and minor abrasion losses.

There have been various products marketed over the years, claiming to be able to be able to dissolve and re-cure the residual finish. In our experience, once the original finish has been compromised, it can’t be restored like this. So, we need to consider other options.

2. Removing the Outer Layer

Having assessed the condition of the finish, we have a strategy. We are going to carefully scrape away the residue of the original outer layer of shellac, leaving the layer of colour behind. Then we can simply replace the shellac with a new layer.

Our weapon of choice, the cabinet scraper.

Our weapon of choice in this is a very thin cabinetmaker’s scraper. Essentially a piece of thick sheet steel about the size of an index card, this tool operates slowly, and provides superior control when removing a finish. While heavier scrapers are available for smoothing wood (ever wondered what was used before sandpaper?), the thin ones are much more gentle, and can be flexed in your hand to suit the width of the area on which we are working.

Old shellac turns to dust.

In the accompanying photos, you can see the results. The dry shellac scrapes off, turning to powder as we go. A gentle hand means that both the colour and the dents and dings that contribute to the patina of the piece are preserved as much as possible.

A portion of old shellac completely scraped away.

We carefully continue until the entire box is clear of shellac, being especially careful around corners (where it is especially easy to remove wood, rather than just finish), and the rounded box corners (where the wood fibres could be caught and torn by the scraper, should we be using it in the wrong direction, against the grain). We also remove the burlap from the bottom of the box.

As a final step, we dampen a clean cloth with alcohol, and paint the entire area with it. Oak has very open pores, and shellac dust has gotten in all of those nooks and crannies. This step will serve to re-dissolve this residue, in effect giving the whole thing a very thin base coat of the original shellac.

3. The New Finish

Now we can lay down shellac over the original colour. The secret of fine shellac finishes is many thin layers, with a good curing time between each. Alcohol evaporates very quickly, and a thick layer invariably ends up looking gobbed or stripey. So, thin it is. We like to use shellac about the consistency of maple syrup, which means buying it in flakes and mixing it ourselves. If you want a job done right, do it yourself with materials you have processed yourself, as much as possible!

New shellac gives a warm glow.

We brush it on quickly and surely, and leave each coat until it is fully cured, and lightly rub it with extra-fine steel wool between each coat. (We like to use continuous-strand steel wool; it doesn’t leave behind and bits of steel, although we still wipe it clean after rubbing.) This serves to smooth any bits and pieces that may accidentally become embedded in the finish while it is drying. You don’t want a piece of grit or cat hair lurking under four layers of shellac!

Compared with the original finish.

Four or five coats looks about right. We compare it with the original finish, still intact on the tray. The tray is lighter in colour, but that is to be expected. ultraviolet light (sunlight) always darkens the patterns in the figure of wood. So, any internal fittings will always be lighter in colour. In this case, we are looking for similar thickness and sheen. Again, the tray is perfect and shiny, and the exterior is not. We could polish the exterior up between coats, like a French polish, but this box needs to remind people that it is old, and has been handled regularly for a century. So, the outside will not be as perfect as the protected interior fittings, and we like it like that.

We will leave the final rubbing with wax paste for the very end, after the box has been entirely re-assembled. But for now, we can move on to the next step: the hardware.

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