This is post no.20 of #BlogchatterA2Z.
This includes blogging every day in April for 26 days, except on Sundays. What’s special about it is that every day’s post will be corresponding to each letter of the alphabet.
All my #BlogchatterA2Z posts 2021 can be found here.
Did you know that when we use sellotape (or Scotch tape in US English) to repair tears in the pages of a book, we cause more harm than good?
I didn’t know this and when I found out while researching book terms beginning with “T,” I decided to write about it.
Book and paper conservators are often asked to remove tape marks and residue from old books and documents. They find it a tedious task to remove tape residue and damage to paper by sellotape stains.
As the paper gets older, the tape causes more damage to it.
How Sellotape Damages Paper
Sellotape is a product made of two layers:
a) Top layer – a clear film traditionally made of cellophane. It’s the carrier material. Nowadays, it could be plastic or paper.
b) Bottom layer – a pressure-sensitive adhesive. It is usually made from rubber and sticks to whatever it touches when pressure is applied.
When we apply a bit of sellotape to paper, the pressure-sensitive adhesive sticks to the paper.
Over time, the cellulose in the paper (a type of polymer) and the rubber-based adhesive (another type of polymer) start interacting with each other and begin to get attached. This process is called cross-linking.
This is when the sellotape becomes discolored (deep brown) and insoluble. The paper fibers around the tape also become yellow and oxidized.
The longer the tape stays on the paper, the more discolored it becomes. Together with this reaction, the adhesive also loses its power and the tape carrier (top layer) falls off the paper.
What remains behind on paper is the solid, discolored adhesive.
Thus, what was used to repair the paper has ended up damaging it.
A few other associated types of damage(s) may also occur:
- The weakening of the paper around the area of the tape due to the difference in the thickness, causing tears near the tape.
- At high temperatures, the adhesive can become labile and cause the tape to shift from its place. The exposed area remains sticky and attracts dirt.
- When the sellotaped paper is folded, other areas of paper may also get stuck. Trying to unfold the paper causes tearing and damage.
- Wrinkles may appear around the area of the tape due to differences in dimensional stability and the ability to absorb moisture from the surroundings.
How to remove sellotape residue from paper?
If the tape is relatively fresh and has not had a chance to extensively cross-link with the paper, conservators can still recover the document without much damage.
However, when the tape carrier falls off leaving behind a stain, there’s not much that book conservators can do.
Unfortunately, there’s no one way to remove adhesive and stains from paper because different tapes use different compositions of adhesive.
And these adhesives react differently to heat, light, and humidity as well as the chemical composition of the paper, cloth, leather, or whatever material it has been applied to.
Tape residue is removed from paper in 3 steps:
Backing Material Removal
The backing material is usually carefully scraped off using a fine spatula. Some types of tape like brown gum tape need water to help with removal, whereas masking tape comes off on its own.
Sellotapes can be removed by gently heating with a hair dryer and then teasing with a spatula. This spatula is usually dipped in a solvent to help remove the tape adhesive as well.
Solvents like IMS, acetone, toluene, isopropanol, and ethyl acetate are used to remove the sticky adhesive from the paper, stopping further oxidation.
The solvents cause the remaining adhesive to swell, aiding in its mechanical removal.
Adhesives may also be removed by dry cleaning using cellulose powder or crepe rubbers.
This is the hardest part of tape residue treatment. Rubber adhesives stick to the surface of the paper, but acrylic adhesives can even penetrate the paper. Thus, the adhesive may be removed by solvents, but the stain remains.
What’s done is flush a suitable solvent through the adhesive in a vacuum chamber without getting the paper too wet or allowing it to dry fully. Even if this does not remove the stain, it does remove some of the stickiness.
Watch this video to see how old, yellowed tape is removed from paper: