Soaking and stretching is recommended when lighter weight papers are used with a quantity of water (e.g. 150g/m² (72lb), 190g/m² (90lb), 300g/m² (140lb)), because the paper will move and buckle/cockle. Why does the paper move?
When applying water to paper it moves and buckles (known as cockling by papermakers) because the application of moisture to the sheet will cause one side to expand slightly. However, the other side remains dry, and due to the sizing contained within the sheet does not expand. To counteract this expansion on the wetted side, the paper does the only thing it can and bows and buckles. This is very unsightly for the finished painting and difficult to work with because the paint will pool in the waves of the paper How to soak and stretch watercolour paper
1) Soak a sheet in a tray of clean cold water for:
150g/m² (72lb) - 3 minutes
190g/m² (90lb) - 3 minutes
300g/m² (140lb) - 8 minutes
Take care not to touch the area you intend to paint (the paper is fragile when wet and finger marks will show up in the wash).
2) Drain the paper and place the soaked sheet on a sturdy board (we recommend Marine Ply).
3) Blot any excess puddles of water with a clean paper towel. 4) Wet some gummed tape with a sponge or large paint brush (do not soak), and place around all four edges of the paper, and leave to dry on a slight tilt.
5) Leave the paper to dry overnight. When dry the paper will be stretched tight on the board and when water is added with the paint the paper will not move. Important
When soaking the paper it is very important NOT to accidentally contaminate the paper with residue detergents found in areas like baths, kitchen sinks. These detergents attack the sizing causing the paper to become very absorbent and unusable. Trouble shooting
Tape pulls away from paper when the paper is drying
- It is possible the gummed tape has been wetted too long removing too much glue.
- There isn’t sufficient glue on the tape to hold the paper tight when drying.
- There is a problem with the absorbency of the paper (either accidentally induced with detergents (see above) or during manufacturing), which has caused the paper to soak up too much water that makes it difficult for the tape to stick to the paper. The paper acts like blotting paper after soaking, but is fine unsoaked
- The most likely explanation is the paper has been contaminated with detergents. Unfortunately detergent residue is often found in areas commonly used for soaking paper like the bath or kitchen sink. Unfortunately detergents attack the sizing causing the paper to become very absorbent and unusable. Dark marks are appearing in the wash
- Usually dark marks that appear in the wash are often attributed to finger marks when handling the paper. The paper is especially fragile when being soaked so it is very important to handle the paper with care by the edges. Thin white lines are appearing in the wash
- Thin white lines are usually caused by a puddle of water being left to dry on the paper. The puddle dries leaving a 'tide mark' which shows up as a white line after application of a watercolour wash. The paper isn't as strong after soaking and stretching
- If the paper is soaked for too long the gelatine surface can be washed from the sheet. Historically handmade paper with a heavy surface sizing of animal skin glue needed to be soaked for a long time, this is no longer the case on modern mould made papers and soaking for excessively long periods can reduce the effectiveness of the paper.
How to avoid soaking and stretching
- Use a heavier weight paper. 425g/m² or above should not require stretching. The paper is thick enough to withstand the moisture applied to it without buckling/cockling too much. The heavier the paper the less it will move.
- Use a watercolour block. Blocks are glued on all four sides pulling the paper tight so it resists buckling/cockling.
| 