This is post #7 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.
Do you remember the translucent sheets of paper that separate photo plates from the other pages in a book?
That’s glassine paper.
Glassine paper is a smooth, translucent, and glossy paper that is resistant to air, water, and grease.
However, glassine is NOT waterproof. If you pour water on it, it will absorb water and become soggy.
Traditionally, it is used to store drawings, maps, watercolors, etchings, or prints.
Glassine paper is often mistaken for wax paper, plastic, or parchment but it is a 100% wood pulp product. Perhaps its name is derived from its glassy smooth look and feel.
Features of Glassine Paper
Some characteristics of glassine paper make it useful for a variety of uses:
- It is pH neutral and acid-free because of its manufacturing process. (more on that in a bit)
- It is 100% recyclable and biodegradable. (how green is it?)
- It has a smooth, unbuffered surface on both sides.
- It is available in densities between 40 GSM and 90 GSM. This is more than twice as dense as other common types of paper.
- It can be dyed to give it color or treated with additives like calcium carbonate, titanium dioxide, or clay to make it opaque.
What is Glassine Paper Used For?
The uses of glassine paper are manifold—and not just in book preservation:
Interleaved glassine paper is used to protect photos or illustrations from touching the page facing it. It can be manufactured to give it a neutral pH to protect it from rubbing and spilling.
Traditional photo albums
This may be an easily recognizable use of glassine paper. It is used to protect photos from sticking to each other and other types of damage. It also gives the photo album an aesthetic look.
Glassine paper is used to repair books and protect acrylic paintings during storage and transport.
Philatelists use glassine paper to make envelopes to store stamps and stamp hinges because of its translucent quality.
Gift bags made of glassine paper are used by businesses, hobbyists, and crafters to wrap products and gifts or create crafts.
Due to its greaseproof quality, it is used to line baking trays and tins, wrap cheese and meat, and make bags to carry bakery goods.
How is Glassine Paper Manufactured?
The wood of hardwood trees such as birch, gum, oak, and aspen is used to make glassine paper.
Logs of wood are cut into tiny pieces in a chipper to be ready for chemical or mechanical pulping.
The wood chips are treated with different ion solutions under pressure to convert them into paper pulp, which is a fibrous material. Pulping breaks down the chemical bonds of lignin, a substance in wood that gives it its stiffness. It also separates cellulose from lignin—two polymeric substances present in wood.
It’s important to remove all the lignin from the pulp to make good quality glassine paper. Otherwise, the lignin in the pulp will react with the bleach, making the resultant paper brittle and yellow over time.
When lignin is fully removed, the paper produced is pH neutral and has greater resistance to changes in its optical, chemical, or structural properties.
These properties make glassine paper different from other types of paper.
The wood fibers that remain after pulping are treated with bleach, pigments, dyes, or additives to create the required grade and color of paper.
A moving wire cloth in a paper machine drains most of the water in the treated paper slurry. Sheets of paper are formed by intertwining of the fibers in the slurring and matting.
The damp mat moves through a series of roller presses to remove the remaining water (supercalendering).
The final step is to move the damp paper through the dryer section to create dry sheets.
Calendering is the last step of the papermaking process before the sheets are cut to the required size. Calendars are rollers or hard pressure cylinders used to smooth the surface of paper by pressing the sheets between them.
After the sheets of paper have been thinned by calendaring, another set of rollers called supercalenders are used to make the paper even more smooth and shiny. This paper is called supercalendered paper or SC paper.
The supercalender is made up of alternating cylinders of polished metal and a soft resilient surface (called nip). It runs at high speed and glazes both sides of the paper by applying heat, pressure, and friction.
Supercalendering breaks down the capillaries of the paper fibers, making its surface closed, improving its density, and reducing its porosity. This gives the paper its water, grease, and air resistant properties.
The degree and quality of supercalendering affects the density and translucent quality of the paper. Thus, cheaply made glassine paper is less translucent.
Other types of papers are usually coated with wax or plastic laminates to make them resistant, but this makes them less biodegradable. Thus, glassine paper is an eco-friendly alternative to these papers.
Printing on Glassine Paper
Due to its smooth and glossy surface, it is difficult to print on glassine paper. Inks tend to smudge during or after printing because the paper is less porous and the ink takes longer to dry.
Thus, it takes considerable experience and expertise to print properly on glassine paper.
Embossing is also difficult on glassine paper because it tends to crinkle and shift during the printing process.