Advice Needed: Methylcellulose vs Carboxymethylcellulose vs Sodium Carboxymethylcellulose

I know that methylcellulose is often used in paper and cloth conservation processes. I also know that a PVA-mix with methylcellulose is in use by bookbinders — that mix allows lengthening of the time of drying of the PVA glue. I’ve even used the mix myself while I was studying at the American Academy of Bookbinding. However, since the time of my study I still haven’t bought any methylcellulose here in Moscow.

The main obstacle to buying methylcellulose was that most local vendors sell it only by hundredweight or even a ton! I don’t think I’ll use as much mix in a lifetime!

Talas is too far away. However, there is a shop for conservators, which offers methylcellulose and similar polymers. However, methylcellulose itself is not available now.

Can you tell if there is any difference between methylcellulose, carboxymethylcellulose and sodium carboxymethylcellulose if you plan to use it in the PVA-mix? Or they are the same thing and I just don’t need to worry?

I would be really grateful if you tell me if there is any difference between these polymers at all? Besides the chemical formula, of course.

Update: Several links I’ve received at our Facebook page: