Step-by-step guide to stretching Watercolour Paper - my method anyway.

Materials required:

A number of strong wooden boards (the pull of the a full sheet of drying paper is immense) for each size of paper (quarter, half and full Imperial - for the most economical use of the paper). I have boards dedicated to each size.

Watercolour Paper:
Cut to the size (if needed).

Brown Gum Paper Tape:
50mm/2" wide.
Note: masking tape is not really strong enough for larger/thicker sheets.
An alternative is to use a staple gun and staple around the edges.

Tray or Bath:
Needs to be bigger than the sheet of paper

Enough to cover paper

Place a sheet of watercolour paper (fully submerged) in a bath (or tray) of cold water for a few minutes (10 to 25 at the most, give heavy paper near the upper end of this time). The paper needs time to expand.

While the paper is soaking cut the gum tape to a length longer than the paper.

Check the board is free from any protrusions/dirt that 'will' show when the paper is dry.

Remove the paper from the water and hold vertical while the majority of the water drains off.

Then place the paper centrally on the board.

To wet the gum tape, dip one of the four pieces into the water and then lift out of the water and holding one end, using your other hand run the full length of the tape between two fingers stopping at the other end (this removes most of the water). Note: most tapes will try to curl at this point but you'll have hold of both ends.

Next place the tape to cover the paper by 15 mm (1/2"). This is best done by positioning one end down on the board while holding the other end clear and then as you lower the second end, line it up with the first end.

Run your hand over the tape to push it down onto board and paper. Repeat for the other three sides.

Leave the board flat in a location that is away from being walked on/over, anything jumping on it (pets etc) or near a heat source (it needs to dry slowly for a number of hours - best overnight). This time factor is the main reason for having a number of boards with paper stretched and ready for painting. And yes, the odd error will happen, tape splitting etc, even after years of practice.

Paper and Gum Tape Removal:
With a sharp knife, run it around the very edge/lip of the paper (cutting through the gum tape only). Do one of the long edges first, then a short edge to release some of the tension. While cutting, the gum tape may, split or crack due to the release of the tension (it is normal).

When the watercolour paper has been removed a small lip is left on the gum tape that's remained stuck to the board allowing you to pull most of the tape off (pull from lip edge side across the width of the tape - inside to outside).

I leave the rest on until six or more painting have been done, but only if the previous layers of tape are solid. Not only does it provide a guide for the placing of the tape for the next painting (using one size of painting on each board) but is easier to remove when there's more layers.

For a total removal of all the gum tape from the board, soak in water, which can be done in between each painting.

The gum tape remaining around the painting border can be removed by cutting it off.