How did buying watercolour paper come to be so confusing? At first glance its specification reads like a scientific formula: 300g/m2(140lb)HP. Do I need NOT or Rough? Cold pressed, soft pressed or hot pressed? Paper, a block or a pad?
OK, let’s take it as you’d eat an elephant (though I hope you wouldn’t), one bite at a time.
Watercolour paper traditionally comes in three surfaces: Hot Pressed (HP), Cold Pressed (CP) – which is also called NOT – and Rough. Hot Pressed is the smoothest. That’s easy to remember if you imagine doing the ironing. (No, I try not to think about that either, but it’s a useful analogy for this purpose, so please bear with me.) If you pressed the paper with a hot iron it would be as smooth as possible. That’s Hot Pressed, the smoothest.
Next comes Cold Pressed. If you used a cold iron the paper wouldn’t be quite as smooth as using a hot iron, so that’s Cold Pressed, a medium texture.
Rough – sorry, no prizes for guessing this one – is the roughest texture.
Recently Fabriano have introduced Soft Pressed. That surface comes in between HP and CP.
Now for the numbers. Watercolour paper is measured by the weight of 500 sheets of paper at Imperial size (20”x30”). The basic premise is the bigger the number, the thicker the paper. A 90lb paper is quite flimsy, akin to the thickness of two sheets of photocopy paper. 140lb is a medium thickness suited to general purpose usage and 300lb is as thick as cardboard.
Beware, imperial vs metric starts to confuse things, especially if one manufacturer gives the imperial and another specifies metric. Instead of pounds, the metric measurement is grammes per square metre, written as g/m2 or gsm. Here are the equivalents: 90lb=190gsm, 140lb=300gsm and 300lb=638gsm. Each paper surface is available in each weight.
Now for paper, blocks and pads. Paper is available in sheets or rolls that the artist cuts to size. Sheets are usually sold in Imperial size or sometimes in half or quarter sheets.
Pads are either spiral bound or glued along one edge with a card cover. The cover is often emblazoned with the manufacturer’s branding and should also inform the buyer of the specification of the paper.
A block is glued around all four edges with a small section left unglued, usually in one corner. Once the painting on the top sheet has been completed, the artist inserts a blade in to the unglued part and slides the blade around all four sides, revealing a fresh sheet underneath.
I hope that has demystified the basics of watercolour paper, though we haven’t yet looked at deckle edged, rag-made, internally/externally sized, watermarked… we’ll save that for another day.