Most of the collage I do is done with Acrylic Gel Mediums, either glossy or matte finish. I started with Golden's because everyone else was saying it was the best, but I have also used Dick Blick products which are less expensive and seem to be well able to do anything I ask of it.
Many of us who do altered books and collages, find that the acrylic gel mediums have a tendency to stick to the next page. You can never quite tell when it's going to do this. I thought it was the humidity - but I just read somewhere that it is actually heat that is "melting" it. Whatever the cause, it is a sticky situation to have to peel apart two pages of precious art, only to have part of it pull off on the other page.
At first when I experienced this, I used (1.) wax paper as a divider between pages. Then I had the idea to rub the pages with the wax. Over and over again, to give it a wonderfully light wax coating. This works. For me. One of the groups started posting messages about using (2.) Dorland's Wax. I bought it. It works. For me. (3.) I bought shoe polish. Have not tried it yet. (4.) I bought deli wrap, thanks to the prompting of lots of people. I love it to put between pages while they dry, and even later when things are stored. It gives me a feeling of security, knowing the pages will be perfect when they are separated. (5.) I have used spray sealer on the pages. It works. Usually. (6.) I sometimes add something thicker to separate areas that are stubbornly sticky. Something like a button, jewelry, sand, fabric, ribbon, ets. (7.) Another way to help the pages stay separate is to dust them with a light coating of corn startch or talcum powder. I have not tried this, as the other methods are working for me, but I mention it in case you want to try a different method.