I have had countless problems with pastel fixatives and I have totally ruined many a good painting by using too much of the stuff.
The first solution here is to use as little as you can get away with. Even the absolute best quality fixatives will tend to have a slight dulling effect on the colours and, if you use too much, you will make the surface "frosted" - or even shiny. (And it's quite difficult to apply pastels to a shiny surface!) I want the fixative to bind the pastel particles sufficiently to be able to add a subsequent layer - and nothing more. For this reason, I never use fixative on the final layer... This helps to maintain the vibrancy of the final layer of pastel on the painting. If you choose to follow this method, just be very careful with the painting until you can get it framed behind glass...
Building up a pastel painting with several layers - as long as you don't overdo the fixatives - can actually make the painting more vibrant. Unfortunately, though, it's quite hard to build your layers if you are not fixing between the layers...
My advice here is to simply go for the very highest quality product that you can lay your hands on... For one thing, the price of a very high-quality pastel fixative will put you off using too much of it!! And you will stand much less chance of getting any very undesirable "frosting" effects if you do accidentally use too much.
My fixative of choice is the one made for pastels by Senellier. (Senellier also do a very similar fixative which has been formulated especially for charcoal drawings. I find that it also works very well with pastels but it does seem to be a bit lighter - and so you really need to use more of it when working with pastels...)
I can not get hold of Senellier fixative in the Philippines but I find that the museum grade varnish, satin, produced by "Golden" suits my purposes quite well. The only real problem that I have with the Golden varnish is that it takes quite a while to dry.
But then again, that usually gives me a good excuse to go out for a beer!
I buy my Golden varnish at Diovir in Santa Cruz, Manila
I wouldn't touch any of the other so-called fixatives that you can buy in National Bookstore, with a bargepole!!
Edited by smb