Just because two documents have been folded doesn’t mean they’ll behave the same way. One might open easily and return to its shape. The other may crackle along the fold line before you’ve even opened it by a centimetre. They may look identical, which is why flattening should start with careful examination, not the application of pressure.
If paper is flexible, it won’t crack, flake or whiten visibly when the fold line is moved. Brittle paper may feel stiff, or break at the edges or crumble to dust if the backing support underneath it is moved. Don’t check flexibility by folding back and forth in the same spot. Lay the document on a firm surface and see what happens when the support is moved. Pre-existing damage such as cracks, missing edges, tape and tight folds can indicate that unfolding the document will cause further damage.
A fold isn’t necessarily a problem that needs to be undone. It might give information about the history of the document, such as how it was folded up for mailing, folded away into a map case or folded over to protect the content. There are many ways that flattening a document can cause further harm. A creased document can be torn apart by the process of flattening, writing can be smudged, parts can be dislodged or there may be an increase in stress to any existing repairs. Methods that use water introduce risks such as cockling, tide lines, pigment migration and differential swelling.
Try out the process of flattening on waste paper before you try on your document. Fold a piece of modern flexible paper and a piece of paper that has been dried and is fragile. Fully support both sheets and open them only as far as they will go without being forced. Note if the crease relaxes, stays as a sharp fold, becomes white or starts to crack. Don’t try to get the paper to lie completely flat if it doesn’t want to.
Learning to accept that a document may not lie completely flat is part of the skill set of a conservator. A document that is only partially flattened may be safer than one that has been aggressively pressed flat. You can also improve the protection given to a document without affecting its shape. An oversized archival folder, a box, interleaving or even just carefully placing the document among others can minimise the risk of it being caught by another document while it’s stored, without changing the appearance of the fold.
Some people talk about using weights, blotters, release paper or humidity to flatten paper. These techniques shouldn’t be seen as the one size fits all solution to flattening. They can work well for some types of paper, media and types of damage but don’t work well for others. Water-sensitive paper, wet paper, paper with glued-down elements and paper with structural damage require specialist attention. Severely brittle paper, stuck sheets, fugitive inks, mould and large tears should be referred to a professional conservator.
Before flattening old paper, ask yourself what the flattening is supposed to achieve. Does the fold present a safety hazard for the paper? Or is it just an aesthetic issue? Is the paper flexible enough to be opened without causing damage? Would better storage protect the paper from damage, without changing its shape? If you can’t answer these questions with certainty, then choosing not to flatten the paper doesn’t mean you’ve failed to save the document, but that you’ve made a conservative decision about the level of risk.
