Unfortunately i don't live in an area where birch are all that common and couldn't find any burls on other pieces of wood. This resulted in a slightly square looking cup as i had to use a straight grained piece of beech.
The end result looked nice but i had a few issues with splits along the way, and a few cracks in the finished product.
As with most things i tried to used the very simplest of tools, things that you could use in the bush to create what you need, though with this project i did cheat a little bit and used an electric sander to do some of the rough sanding.
Materials and tools:
Wood- preferably a birch burl (burls can also be found on most species of tree, olive and walnut give great results.)
Saw- to trim up the log.
Axe- for rough shaping, much quicker and easier than using a saw in my opinion.
Hook knife- for carving out the bowl of the cup.
Knife- to clean up some of the rougher shaping.
Sandpaper (electric sander)- i used grades 60, 80, 100 and 150 for sanding.
Sanding sponges- grades 180 and 240 for fine sanding.
Pan, salt and water- to boil kuksa to remove tannins from the wood.
Oil, cloth- i used olive oil as it doesn't contaminate whatever you have in the cup, unlike linseed.
Step 1: Basic Shaping
Holding the cup end and cutting away from my self (remember your axe should be as sharp as your razor so always be careful) i cut away the area between the bowl and handle giving the cup shape. I then used a saw to cut through above the handle freeing the roughly shaped cup from the rest of the log.
Using a smaller axe, for better control, i gave a vague shape to the outside of the bowl and the area where the handle would be.
Finally i used a knife to clean up the top and give a smooth surface to make the next step easier.
Step 2: Shaping the Bowl
The idea with a hook knife is to brace your thumb or finger on the back of the blade (blunt side) and cut across the grain of the wood. This will remove bits of wood until a bowl starts to appear, now just try to deepen the bowl and work at the sides.
This may take a while, particularly with a wood as hard as beech.
Once your happy with the depth and width of your bowl its time to start sanding.
Step 3: Finer Shaping/ Rough Sanding
Because of how hard the wood was and the awkwardness of the shape of some of the parts (meaning i could't get the spoke shave in to smooth the off) i ended up using an electric sander with a P60 pad on to do most of the rough sanding.
After a good 2 or 3 hours (and many sanding pads) i was finally happy with the overall shape and smoothness.
During this time a split opened up in the handle taking a good 1/2 inch of wood off the side, a quick tap with the axe and some more sanding soon evened up the handle. Although it was now much thinner than i'd intended.
Step 4: More Sanding
After about 10 mins i'd been relegated to sitting on the floor by the fireplace so i didn't get dust everywhere (make sure you've got the hoover handy and you live with understanding people.)
Sanding always takes a long time, but persevere the more you do the better result you'll have.
For sanding inside the bowl i found folding the paper into a wedge works well and allows you to get into all the awkward spaces.
Step 5: Boiling
To boil i filled a pan with hot water and lots of salt, not so much as to reach saturation level but a considerable amount. I then boiled the cup for a little over an hour, you should be able to see the brown tannins staining the water.
You now need to let the wood dry out, i left my on the windowsill all week until it was totally dry.
Step 6: Even More Sanding
You could always use a mix of pva glue and sawdust to fill any gaps.
For this round of sanding i used a P150 paper, the a P180 sanding sponge and finally a P240 sponge. I found these sponges really useful for getting into the bowl of the cup, and the high grading gave an excellent finish to the wood.
This stage of sanding only took me around 2 hours, the wood felt like it had been softened up by the boiling process.
Step 7: Oiling
For this i used olive oil, but sunflower or vegetable are also good choices.
Pour some oil into a bowl and using a clean rag wipe it around the surface of the cup, covering everything.
Leave to dry for a few hours, and repeat a good few times.
I applied the oil 6 or 7 times over a few days. Don't be afraid to use lots of oil, if you use too much you can always just wipe it off the surface.
Once the cup is oiled for the final time you'll have your finished product.
Step 8: Finishing Touches
Using a clean rag wipe away any oily residue, leaving your beautiful kuksa ready to use.
(I also thought about adding a leather loop round the handle but couldn't find any suitable bits of leather)
Now crack open a whiskey and toast to your wood working skills.