Working with Burl and Heavily Spalted Wood - How to Fill and Finish Bark Pockets, Checks & Voids The Easy Way
Working with burls, and heavily spalted woods can involve a little extra work to bring out it's full potential. This guide deals with a commonly asked question; "How do I fill and finish wood that has bark pockets, voids and checks?"
This page shows step by step instructions with photos to show how I do it. You can take things a little further than I did to get a perfect glass like finish but this guide is just to show the basics. You can decide how far to go with your own projects.
The tools and materials you need are probably already in your workshop. Here is what I used; belt sander, palm sander, thin CA glue (super glue is the same stuff), medium CA glue, 2 part epoxy, sanding dust (from the dust collecting bag on the belt sander), 0000 XFine steel wool, spray lacquer (I used an aerosol can).
Disclaimer: I used materials that were close by and did a quick and dirty job just to show you how to do things. The sanding dust was what happened to be in the bag. It is darker than should have been used but it shows up good for the photos. It is best to use dust from the same type wood to blend better unless you want a contrast. The plug I cut should have been cut better to fit the shape of the big void. If you slow down and pay attention to details you can make things turn out perfect.
For this guide I chose a thin piece of spalted maple burl that had soft areas, checks, voids and bark pockets. Guitar builders and fine furniture makers will use thin wood like this and glue it to the surface of a plain wood backing. (if that is what you are doing it would probably be best to do that first) These same steps work real good on thicker pieces. For a rustic look you can skip some of the steps, for a perfect finish you can go a few steps further.
The first thing we will deal with is the big void. Instead of trimming this section away, you can cut a plug to fill the void. It is up to you whether you want to clean up the edges and cut a piece for an exact fit, or use a freeform shape to make it look like an area where a branch was coming through. You get to decide if you want to hide it or use it as an accent.
Here I positioned the void over a scrap piece of similar wood and drew an outline. (It would have been a better fit if I had trimmed away the beveled areas and cleaned up the shape of the void.) You can either try to match the grain for a less obvious plug or go with a different grain to make it look like a branch or knot cross section. Smaller voids you can use a darker plug and sanding dust to make it look like a bark pocket. With burl the grain does such weird stuff that most of the time that you do a plug, people will not know that it wasn't a natural part of the burl.
This is the plug I cut set into the void. If you want to reshape the plug for a better fit this is the time to do so. I used a piece of masking tape to hold it in place. Then I flipped it over and placed a couple pieces of tape to keep the epoxy from running through the wood when it is applied. After that I flipped the wood over and removed the tape from the front.
Next step is to place more masking tape on the backside. I put a piece of tape everywhere that there was a check, void or bark pocket. This is to keep the glue and epoxy from running through the wood and gluing it to whatever the piece is sitting on. Helps to keep things from getting too messy this way.
In this photo I used thin CA glue and saturated any place that there was a check, softer wood or bark pockets. This helps to harden the wood and to secure the bark in place. I used the thin CA glue for this because it penetrates further into the wood. This step was for hardening and securing any loose or soft stuff. We will get to the filling next. (For wood where there is a lot of soft area you can use the thin CA glue and cover the entire surface. This helps even up the hardness so you get a more even finish later.)
While the glue was drying (with CA glue it is real quick) I mixed some 2 part epoxy with some sanding dust from the dust bag on my belt sander. In this case I just used what was in there. (It is usually best to use sanding dust from the same type of wood you are using if you want the fills to blend with the wood.) When you are filling bark pockets or want your fills to contrast the wood, use darker sanding dust from walnut or another dark color wood.
After the epoxy and sanding dust was mixed together, I started gooping it on everywhere that there was a check, void or bark pocket. I used a scrap piece of thin wood to apply the mix where it was needed. The epoxy settles into the low spots after a few minutes. Time to mix some more to apply to all the low spots. You will probably have to do this 2 or 3 times depending on what the wood is like that you are working with. The photo below shows the wood after I gooped on the 3rd layer. The important thing is to make sure there are no spots where the epoxy has sunk below the surface level of the wood after it has dried.
I started to sand with my palm sander but changed my mind. Since I had gooped on the epoxy so thick, I decided it would be quicker to use my beltsander with 120 grit to remove the epoxy from the surface. After most of the surface epoxy was sanded away I switched to my palm sander with 120, then 220 and finished with 320 grit. For a glass like finish you will want to go even finer. Now that everything is sanded smooth it is time to check to see if you missed any holes or low spots. It is up to you whether how it looks is something you can live with or if you should fix any you find. You can do it real quick with Gel CA glue and then re-sand that spot. The CA glue dries real fast so the extra step really doesn't slow you down that much. (It is good to have a little tube of the Gel CA glue around for times like this. You can get a small tube of Gel Super Glue for about $2 at the hardware store.)(If you want a glass finish like on a guitar this is the time to apply a pore filler or sandable sealer and re-sand to a finer grit.)
I like to use Spray Lacquer in an aerosol can. That way I don't have to use a sprayer or have a big mess to clean up. I use Rudd On-Site Clear Lacquer in a Satin finish. It only takes a few minutes to dry in between coats. If I am in a real hurry I can speed up the drying to about a minute using a blow dryer for hair. When using an aerosol finish here are 2 quick hints that will save you a lot of headaches.
#1 If it is cold let the can warm up in front of a heater for a while. Just close enough so it gets warm. Not so hot that the can explodes.
#2 Spray several light even coats instead of a couple heavy ones. This will help avoid runs and orange peel.
After the first coat dries (usually about 10 minutes) rub the surface lightly with 0000 XFine steel wool. Blow off all the residue then apply the next coat of lacquer. Repeat until you like the way everything looks. The photo below shows the wood after 3 coats of lacquer using steelwool in between coats. Pretty good for a quicky job.
Remember, this would have looked a whole lot better if I had;
#1 Shaped the void and cut a more accurate plug.
#2 Used sanding dust from the same type of wood instead of darker stuff.
#3 Applied a pore filler/sanding sealer and sanded finer before applying the lacquer.
The furniture we make is more rustic and organic looking than what is made by traditional woodworkers. The steps above show you how to do things for our type projects as well as explain how to go the extra steps for really fine finishes. I hope this helps, because if it does it will open up a whole new realm of woodworking for you.
If you would rather here people say; "that is the most bizarre wood I have ever seen" instead of; "isn't that pretty", then you need to try this out yourself.
This is a lot easier to do than it sounds.
If there is anything you can use from this guide, please take a moment to click the button that says it was helpful. Thank You
For some really unusual wood, you might want to check out our ebay store It's a Burl