Smoothing Out Onion Skin Paper

Dear Donia,
What is the best way to remove wrinkles from onion skin paper without damaging the paper? 

Onion Skin Paper

 

Q. Dear Donia,

I have a customer with a document from 1971 on onion skin paper that appears thinner than nine pounds and has wrinkles which he would like smoothed out. What is the best way to remove the wrinkles without damaging the paper? We have a wet mount mounting machine (we use archival spray mount) and there is no heat involved. Thank you, Gladys
 

A. Dear Gladys,

The term onion skin paper covers a lot of different translucent papers used for tracing and carrying carbon papers for typewriters. The production varies so fibers and fillers will be different for each paper which means the way the paper will react will be different so it is difficult to describe the best way to remove wrinkles without actually seeing the paper. I would avoid heat as well as excessive moisture. You can try a gentle humidification and flattening process—work very slowly and be vigilant as onion skin papers can react very strangely when humidified.

 
Humidification
 
Necessary Supplies: 
  • A large, long, shallow bin with a tight fitting lid (for example, an under-the-bed storage bin)
  • Nylon window screening (easily found at your local hardware store)
  • Spun polyester—Hollytex is very smooth and will not imprint on the emulsion. Hollytex can be purchased by the yard from Talas—product number 3249 would be the best choice.

Begin the humidification process early in the day. It may take several hours, and objects should never be left in the chamber overnight. 

Using a plastic bin:
  • Line the bottom of the bin with a damp towel (use cold water). Any excess water should be removed from the towel by wringing it out. 
  • Place 4-5 layers of nylon window screening on top of the damp towel.
  • Place a piece of spun polyester on top of the screening.
  • Place the rolled or folded items on top of the polyester.
  • Fasten the lid. 
  • Wait. Check the items after about an hour. If they are not completely relaxed, replace lid, wait another hour, and check again. Repeat until the items have relaxed.
Do not leave objects in a humidity chamber for more than eight hours as this can lead to mold growth.  
 
Flattening
 
Necessary Supplies: 
  • Sheets of clean blotting paper—10 point blotter paper can be purchased by the sheet from Talas
  • Spun polyester 
  • Stiff, smooth material like Plexiglas or Masonite the same size or larger than the blotters
  • Weights such as bricks
Procedure:
 
Remove the relaxed onion skin from the humidification chamber and place the item on a piece of dry blotting paper lined with a piece of spun polyester. Handle item carefully: damp lightweight paper can be fragile, especially if it is already damaged in some way. Place in a flattening/drying package (see list below). If using wood products for the top board, it must be flat and smooth, without any warping. Weight with bricks. Use just enough to provide some restraint but not so many that would crush the paper. Leave weighted until dry—at least 24 hours. 
  • Brick
  • Plexi/Masonite board
  • Blotter
  • Hollytex
  • Photos
  • Hollytex
  • Blotter
  • Level, smooth table top
Although most paper can be safely humidified,onion skin paper can react oddly so extra care is necessary during flattening. Please be sure to use caution at each step so that you don't damage the item. Taking it slowly will allow you to monitor and catch any problems early.
 
Thank you for your question, and please don't hesitate to ask if you have any more.