Using gum tragacanth to burnish makes getting smooth, consistent leather edges easy. People use different edge-finishing products like CMC, Tokonole, Magic Edge, etc. I like it because it is readily available, simple, and gives nice-looking, fast results. In online discussions, people will abbreviate it to ‘gum trac,’ they are the same thing. If you need help or are thinking of trying out gum tragacanth, I’ll go over how to use it so you can get the best results.
What is Gum Tragacanth?
Gum tragacanth is a natural gum that comes from the dried sap of plants in the genus Astragalus. The name derives from the Greek words tragos (goat) and akantha (thorn), a common name for the plant goat’s thorn. This might seem like boring technical detail, but knowing that gum trac is… well, a gum will help you to understand how it works.
The raw gum is extracted and dried from the plant. It is typically concentrated into a liquid. The resulting product is water-based and can be used as a thickener, stiffener, and for leather burnishing. The latter is what most leatherworkers use it for.
Many people think of gum trac as just a lubricant for burnishing. It is indeed that when wet. Unlike alternatives like water, however, when gum trac dries, it leaves behind the gum to bind leather and smooth the surface.
Is gum tragacanth safe? Yes. It was historically used in herbal remedies and as a topical burn treatment. There is no modern evidence this is useful, and while it’s not toxic, I wouldn’t eat it.
When to use Gum Tragacanth
Use it to moderately harden and smooth edges – Since it is a gum, it acts as a thickener and helps when burnishing. The goal of edge finishing is to get smooth edges, and the gum fills in the tiny voids in the leather and hardens the edge into a flat surface. Gum tragacanth is still malleable when dry, giving edges some rigidity and preventing cracking when bent.
Use it on vegetable-tanned leather. The vegetable tanning process enables leather to be burnished to a smooth surface. The gum enhances this property and eases the burnishing process. It works somewhat on oil-tanned leather and not at all on chrome-tanned leather. For combination-tanned leather that has been vegetable-tanned and chrome-tanned, gum trac works on a case-by-case basis. It works great on leather like Chromexcel but not on other combination-tanned leathers.
Do not use it as a bare base for paint. If you paint over a smooth, finished edge, the paint will peel faster. Like painting anything like wood, steel, plastic, etc., paint best bonds to a slightly rough surface. I see some people burnishing with gum trac, sanding, and then painting over it, but this is not ideal. The gum trac penetrates the leather edge, smoothing the surface and making it a less suitable painting surface. When painting, you want the paint to penetrate instead. So either sand the surface before painting or skip using gum trac entirely.
Paint is different than dye. Most darker edge paint contains some dye, which will penetrate through a burnished surface, depending on the leather. Denser, waxy leather may reject dye if it has been burnished first, while drier, lighter leather can accept die. It also depends on whether beeswax (no dye penetration) or paraffin wax (allows dye penetration) has been mixed in.
How to Use Gum Tragacanth
A complete tutorial on edge finishing is beyond the scope of this post. Before using gum tragacanth, shape your edge through sanding, beveling, or combining both. You want a nominally smooth edge before burnishing.
All burnishing compounds are finishers, not fixers. This is true if their base is gum, glue, or oil. If you have bumps, low spots, splits, etc. Burnishing edges is analogous to painting walls; there’s surface prep and painting. Gum trac and all edge finishing will somewhat smooth over trouble areas, but there is no substitute for proper edge preparation.
If you’ve prepared your edge, here are the steps for using gum tragacanth:
Apply sparingly. I always tell my students to think butter your bread, but that is quite subjective. Apply it like nail polish.
Let it sit for a little while on the first coat, but don’t let it completely dry out. The goal is to let it penetrate, but you cannot work it into the leather if it completely dries out. When burnishing, you’re listening for a squeak. We’ll return to this, but if your edge is too wet, you’ll never know when it is done.
Clean the excess. Use the drying time to wipe the excess off the face of the leather. The gum will wipe off but is more stubborn if you let it dry out. The burnisher should contact the edge when you burnish it in the next step. It’s a bit of a Goldilocks comparison; it’s not too little, so the burnishing is stuttering, and not too much, so your burnisher doesn’t make contact.
Burnish. Run a wood burnisher over the edge and work the gum trac into the edge. It should be light and fast. Putting more force into the burnishing will create lumps and burn marks in the case of a motorized wheel. I recommend new students to focus on just 1-2 inches at a time.
Look, listen, and feel. Look for a smooth edge and run your finger over it to check for rough spots. A good way to know when to check is that you hear a squeak. When you first start burnishing, there is no sound because the gum is still a liquid working into the leather. When you’ve entirely worked it in, it dries, and the resulting smooth surface will squeak from the friction of running the burnisher over the edge.
Gum Tragacanth vs Tokonole
They are similar but not the same. Tokonole’s first ingredient is white glue. This is helpful in some instances and not in others. I prefer the flexibility of gum tragacanth, but you should decide for yourself.
Gum Tragacanth vs Saliva
You can lick your edges to burnish them. It’s a cheap alternative, but I find it revolting. You don’t need much more if the leather is sufficiently waxy. Spit, water, or nearly anything will give you a smooth edge.
Gum Tragacanth vs Water
Using water or licking produces similar results. It slickens the surface, which makes burnishing easier, but water does not leave anything in the leather like gum trac and other edge finishers do.
Gum Tragacanth vs Paint
Paint and burnishing are apples to oranges in comparison. They are both used in edge-finishing techniques, but painting and dyeing differ. With the abovementioned caveats, you can use gum tragacanth in painting or dyeing.
Make smoother edges
That’s it for the tutorial! It’s simple to use gum tragacanth, but as we know from all crafts, simple is not easy. Understanding how gum tragacanth works and how to apply it will make it easier for you to use and, hopefully, achieve a smooth leather edge.
Where to buy gum tragacanth? You can find it right here in our online store. You’ll get a great quality version, which will help support us so we can create more content to help you master leatherworking.