Prepare the sewing pattern
If the pattern is crumbling remove and throw away the crumbling pieces. If there are pencil markings on the pattern and/or pattern pieces you can erase them using a soft eraser. Be careful not to rip or tear anything. Don’t try to remove ink. Don’t use water on any parts of the pattern to “clean” it.
Make it Acid Free
Most often patterns were printed on acidic paper.
Acid testing pen.
You can test the pattern to determine if the pattern was printed on acidic paper using an acid testing pen. Most likely it was so go ahead and spray the pattern envelope, guide and instruction sheet with “Make it Acid Free”. Don’t soak the paper or cause stains.
Tape or Glue
If the pattern has large holes that can’t be easily repaired with tape you can use an acid-free archival glue to repair the area by gluing the damaged area over a piece of acid-free paper. If the area can be easily replied with tape apply a piece of archival tape over or under the damaged areas.
Storing vintage sewing patterns is extremely important. As they’re already fragile due to age, the acidic papers they’re printed on, usage, light, dust and the environment they’re in.