So I went looking again...Sold out everywhere. Only to be found in other countries and shipping doubles the price
Yes, of course I use impregnation in the kuksa. It must withstand harsh operating conditions. I have not used oil in its pure form for about 2 years, as I have my own composition and technology of impregnation.
So I asked Beloyar if he uses anything to seal the inside of the kuksa, or if it was naturally dense enough not to leak. Beloyar replied with: So they are indeed sealed, and have seen a video on him testing the water proofness, but he does not (obviously) show how he seals the kuksa.