St Cuthberts Mill

Why can a paper lose its sizing?

Sizing is what gives water resistance to a sheet of paper and can also help improve surface strength. All of our papers are internally sized with a neutral/alkaline sizing agent (a.k.d). Others also have a surface size applied. There are different types of sizing depending on what paper you use. Our Saunders Waterford range has a gelatin surface sizing. Bockingford has a starch solution, and Somerset doesn’t have surface sizing.

There are a variety of factors when it comes to a sheet losing its sizing, or the sizing becoming ‘patchy’. The biggest problem is usually contamination of some kind. Numerous types of contamination can cause this.

Soaking and stretching paper in a bath is one example. The sheets sizing can be affected by residue left from shampoo, soaps, etc. These chemicals are detergents which break down the water resistance. This will eat into the sizing and break it down.

Contamination from washing brushes poorly can also cause problems. Here are a few other reasons for a paper becoming overly absorbent and sizing being affected.

Environmental pollution - High temperatures increase chemical reactions. Acids from the environment like air pollution, react and degrade the sizing. Hence all our sheets are buffered with calcium carbonate.

Storage - There are times when older paper may have sizing problems. Especially if not stored correctly. Papers stored in the right conditions are able to last a vast amount of time. Maybe even hundreds of years.

Humidity can cause the sizing to degrade. Moisture in the air can also increase chemical reactions. Over a period of time this can weaken the paper and cause a loss of strength.

Light - Sunlight and UV light can be extremely damaging to paper. These can cause a paper to fade and adversely affect sizing.

Always store paper in a cool dry place, preferably away from direct light.