Picture Framing and Art Preservation/sheepskin
I am framing a very old sheepskin document for a client. We are floating it on a 100% cotten board. I am having trouble with the hinges sticking.They stick at first then once dry if I move the board at all they just pop up. I have tried Linco gummed paper tape, Linco gummed Linen tape and Japanese hinges. None of them seem to hold. I haven't tried pressure sensitive tapes because I know that they are hard to remove over time. This is going in a shadow box and there is no outer mat. What do you suggest to hinge this to the board?
Ah yes, it seems like sheepskin/parchment/vellum* are put on Earth to torment framers. They generally are old with historic and monetary value or represent a very expensive education. For this reason they deserve the best care but their nature makes it very difficult to provide that care.
As you have found, it is difficult to get anything to stick to it. That is because of the natural oils in the skin, which is also what gives it a slightly oily or slick feel. It's like trying to stick something to wax paper.
Fortunately I have a few ideas I have gathered over the years from people smarter than me. In order of preference:
1. Instead of using straight starch paste with rice paper hinges, mix the starch 50/50 with Lascaux. It is an adhesive used a lot by conservators for this sort of thing and can be found at University Products or Talas. Just be sure to weight it well once the hinges are applied and let it sit overnight.
My only hesitation is that I would hate for you to go and buy a container of Lascaux for just one job; it's a bit pricey. On top of that I would hate for you to test out new (new to you anyway) methods on a customer's artwork.
2. Forget about adhesives. Instead use a set of rare earth magnets. They are very strong so you would probably only need small disk-shaped magnets about 1/8" in diameter. Glue four to the mat to correspond to the document's corners, lay the document down and then place the other four magnets and the document will be held in place quite securely with no adhesives touching it.
The magnets will show but they are tiny and you could paint them with acrylic paint to blend into the sheepskin. I would also take one additional step and cut tiny circles of one-ply paper to go between the magnets and the document. Lee Valley Tools is a good source for the magnet or a quick Google search will give you a lot of sources.
3. The third option is a direct contact overlay. Now if you go with this option you must use acrylic instead of glass. Cut a piece of polyester quilt batting, preferably needle punched, slightly smaller than the document and attach it to the background mat. Place the document on top of the batting. When you choose your spacers make sure that they are sized so that the acrylic will make contact with the document and compress it against the batting slightly. Then fit as usual.
This method looks great and is very low risk as long as you use acrylic glazing. If the budget allows for Optium acrylic the effect is just incredible.
*There is a difference between parchment and vellum and I believe it has something to do with what animal it comes from. However I can never keep them straight and just about everyone uses them interchangeably, so I don't worry about the distinctions.