Another type of grain filling is when you’re finishing and have some small imperfections, either from tear-out or from pores in the wood. Ideally, you fix as many of these problems as possible before applying any finish, but sometimes things don’t work out perfectly. This is also basically the method used in French Polishing (though that uses rottenstone rather than sandpaper as the abrasive).

Note that all of the pictures here show about 1 square inch of surface (2.5 cm square), so you can get an idea of the scale of things.

In a Russian olive bowl I’m working on, I had a tiny bit of tear-out near the center of the bowl, as shown above. This wasn’t obvious until I got some shellac on the bowl. I’m going to fill this using shellac and a bit of sanding dust (which is probably going to be mostly shellac, as well, but will include some wood dust).

First I sand very lightly with 400 grit sandpaper. Finer will work, but will take longer. Coarser will leave visible scratches. I try to sand across the depressions, so sanding dust will be deposited in them, but I’ll also use a circular motion when I’m starting because it’s quicker and lets me see what direction will work best.

Then I put a drop of oil (I use tung oil, but linseed oil will work, too) and 4-5 drops of shellac on a piece of folded up cloth. Old t-shirts work great.

The shellac I use is roughly a one-and-a-half pound cut. That is, I dissolve about 2 oz of shellac flakes in 12 oz of alcohol. You can use a heavier cut, but don’t go any lighter.

I rub this mixture onto the sanded area, also working across the tear-out. If you go with the direction of the tear-out, the cloth will tend to pull the dust back out, which is not what you want. You also don’t want to rub enough that the new shellac starts dissolving and removing previous layers of shellac. The idea is to build up the shellac, filling the voids. The oil is there mostly so that the partially cured shellac doesn’t “grab” your pad and get messed up as you’re adding a new layer on top of it (and partially dissolving the previous top layer). A little lubrication goes a long way towards making things work smoothly.

You can also see that the weave of the t-shirt has gotten filled with shellac. I typically use a fresh piece of t-shirt each session, because once the shellac is dried in the fabric, it won’t flex to follow the contours of the surface. You don’t want it dipping into every hollow, since you’re trying to fill those, but you don’t want it stiff as a board, either.

This is a fairly slow process. But each iteration you can see a little progress.

And at some point, the dust is almost entirely filling the voids, and not sitting on the surface. That means you’re getting close. The dust will compact as it gets wet, leaving a smaller void, but the results can look pretty darned good.

My take is that this is almost good enough. I think I’m going to varnish this bowl, which will flatten out the finish a little more, so maybe one more bit of sanding will do the trick. But I’m going to let the shellac cure for a while and then look at it and see. That will also give time for the little bit of oil present to cure, which will make for a tougher finish.

#technique #woodworking

Discuss... Reply to this in the fediverse: @davepolaschek@writing.exchange

I’ve had a couple people ask me my technique for filling the open grain of wood with a contrasting color, so here it is, with a few pictures. I also have a writeup on using shellac to fill grain or minor tear-out in a surface.

First, grain filling is usually only necessary when working with a wood with very open grain. Ash and oak are good examples. But sometimes you will want to fill the grain on a wood like mahogany or khaya. It’s the same technique in both cases.

First is to get the wood sanded smooth, and then to thoroughly wipe off the sanding dust. If you’re filling the grain of the wood with a contrasting color, having that grain partially filled with wood dust from the same wood will lessen the effect. That doesn’t mean that’s not an appropriate technique in some cases, it’s just not what I’m describing here.

If you see that some of the pores still have dust in them, or perhaps even if you don’t, brushing (with the grain) can remove even more of the dust from the pores, leading to a better fill. Both a nylon brush and a wire brush will work, though the effect is different. Thanks to @bento@tinnies.club for suggesting using a brush, which I forgot to mention here on the first edit.

Next is to mix up the grain filler. I use either black or white Wunderfil by Rockler, and then add dyes to the white if I’m after a colored fill. I dilute the Wunderfil with water 50-50 so it’s fairly thin and will flow into the pores of the wood. Some wood fillers need to be diluted with oil, which isn’t as easy to use. Today I used blue milk paint mixed with white Wunderfil. I mixed up the milk paint normally, then mixed that with white Wunderfil with about equal parts of each. Then smear the grain-filler on the wood. I generally put on blue gloves and use my hand, but if you’re working on a flat surface, you can use a squeegee. The important thing is to go across the grain so the fill is pushed into the holes and not wiped back out.

In many cases, after you give the fill a few minutes to dry, you’ll notice that the grain has opened back up, and can take more fill. If that’s the case, apply a second coat over the first. I almost always need a second coat, but it really depends on the wood and what kind of fill you’re using. Safer to apply a coat you don’t need than to leave some pores unfilled, though.

With the second coat on, you want to wait for it to dry. A half hour is generally enough with Wunderfil, but more time won’t hurt. Once it’s dry, you sand back to bare wood, but be careful not to overdo it and sand away all your fill, too. I generally will sand with 400 grit sandpaper, but finer will work too.

At this point, you can begin finishing. I’m going to use a homemade friction-finish made from shellac and tung oil on this pen, so I’ll apply my first coat of tung oil and then wait overnight before moving on to the friction finish. This will give the fill and oil a chance to cure a bit, and makes it less likely the finishing process will pull the fill out of the pores.

You can see how the oil brightened up the colors. If there are spots that aren’t filled completely, you might need to apply more fill at this point (and then sand it back again later), but I generally try to do any more filling before putting on the oil. Sanding back will be messier and the fill may not adhere very well to oiled wood.

Once the blank has had time to cure (at least overnight with tung oil), continue with your finishing regimen. For me, that’ll be two or three coats of an oil and shellac mix, applied at the lathe, and buffed with a cloth so the heat speeds the curing of the oil. That finish will get another day or so to cure before I handle the piece too much.

#woodworking #technique

Techniques

Discuss... Reply to this in the fediverse: @davepolaschek@writing.exchange

Originally written May 2, 2018

I couldn't find anyone describing how to cut dovetails for non-square corners, so I decided to write this up. This trick will work for any angle dovetails, but you'll have to change up the workholding jigs.

This is a description of how to cut dovetails for a 135 degree corner. This is the angle used on an octagonal box (if all the angles are equal). They're not perfect, and there's probably a better way to do it, but this is the best I found.

My first try cutting 135 degree dovetails used no special workholding. I just threw the pieces in the vise and started cutting. I cut tails first and I cut them pretty much as normal, except with the end of the board at a 45 degree angle, so they were pretty easy.

The pins were fairly straight too. This is feeling easy!

But the fit left something to be desired.

So I sat and thought for a bit and decided that maybe I could use a square piece in the corner, all tails, and put pins on the edge pieces that would go into it, and then cut the 45 degree angle afterwards. It couldn't be any worse than the previous attempt, could it?

Well, that worked okay, and I might end up trying that method again, but I'll have to think harder about the grain direction in that corner piece when I do.

So I tried again. Third time's the charm, right?

I cut the tails square this time, just like you would on a normal dovetail. I even gang-cut them two at a time.

Then I cut the pins on a board with the end angled 45 degrees using a jig I made for the purpose. I made the 45 degree end on the board using a miter jack before cutting.

Those came out pretty good I think. They're a little gappy where I went astray with the coping saw while cutting out the waste, but they glued up solid.

Hopefully someone else will learn from this and find it useful. To get the boards to look good in the corner, just make the corner piece (the walnut in the above photo) 0.7 times as thick as the edge piece (the ash). The example I show has the walnut thicker, and the corner looks kinda goofy to my eye.

#technique #woodworking #dovetails

Discuss... Reply to this in the fediverse: @davepolaschek@writing.exchange