It’s the task everybody loves to hate”. So much there are even online support groups for luthiers who go slightly mad with it…
But rather than moaning about it, I would like to look a bit into the history of sanding. It’s often said that historical luthiers didn’t use sandpaper. And it’s true, the first European attempts to make ‘glass paper’ on an industrial scale date back to the 1820’s. But that doesn’t mean that our ancestors didn’t sand…
There are a couple of natural materials that are abrasive enough to sand wood and polish metals etc. Some Ancient Egyptinan murals depict woodworkers, sanding furniture with blocks of sandstone (what’s in a name?) And shark- or dogfish skin was known since Roman times.
While sandstone is too rough to finish instruments, the shark skin is very fine (almost like #1200 wetordry sandpaper. But it’s rather hard to get and quite expensive. So I don’t use it in the shop. Planing and scraping are great methods to get a perfect surface, but sometimes it isn’t what we’re looking for.
But there is another option… And it’s very cheap and easy to get. Because it literally grows by the side of the road. Or at least here in the Netherlands it does in some places. A little green plant, often regarded a weed. It’s name: Equisetum, better known as “Horsetail” or “Heermoes” (Dutch). There are a number of varieties, the larger is called “Schaafstro” (Planing straw) in Dutch. While that one is harder to get, the smaller varieties are all over the place. Just try it when you go for a walk. Pick some horsetail and start sanding the top of a nail. You will soon discover that the fine lines get rubbed out, and it leaves a smooth surface. Don’t do this for too long, sanding through your nail can very painful.
There is quite a variety of sources who refer to “horsetail” or ruff as a sanding material. In earlier times the horsetail was cooked before drying. In the present day it’s often used to brew tea, as it also has medicinal values. So maybe we can combine the functions?
I’ve seen various methods to hold the ruff while sanding. Some cut the stems up in small pieces and stick them to a piece of double-sided tape. Others bundle it to make a “polissoir“, like shown in Roubo’s work on furniture making. But Roubo mentions to use normal grass or straw to make the bundle, not an abrasive like horsetail. As the name suggests, the polissoir is for polishing, not the rougher sanding,
I simply fumble it up to a ball, a sort of tumbleweed. An advantage of this method is that sanding dust is quickly taken away. It doesn’t clog like normal sandpaper.
On my last lutes I’ve used it as a final polish before the finish went on. The Vermeyen was sanded earlier, but the finish of the equisetum was finer and more smooth than the 1200 waterproof (!). On the Bosch I only scraped the ribs with a card scraper (sharp but without a burr) and the equisetum. It works very fast and without the frustrations of normal sandpaper…
The reason it works is that it extracts silicon from the soil and stores it in its stem and branches.
Before you run out to pick some of this marvelous and cheap sanding material, be sure to check whether the local varieties aren’t endangered and protected. Also never pick everything on site. Always leave at least 25% to give it a chance to grow back. This will favor yourself and others in the future.