Hi Alexey
I also use Old brown Glue for gluing shamisen kawahari and find it fantastic. The long open time is great and I’ve never had a skin pull away on me.
At one point I got in touch with Patrick Edwards at Old Brown Glue and I think he said that 10% titanium dioxide wouldn’t affect the gluing qualities. Now I could be wrong on that exact number, and I can’t at the moment remember if that was volume or weight (I think maybe volume). I’m sure you could send them an email to get some thoughts from them. I found them to be very helpful and interested. i’m sure they’d be delighted to hear of another shamisen maker using their glue for skin gluing.
For my part, I never ended up using the titanium dioxide as I ended up liking the random transparency that comes from the glue used as it is.
Cheers and all the best!
Would love to hear how it works for you.
Cath