Watercolour paper and what you need to know.

Last weekend I attended a watercolour painting class in support of a friend who was tutoring. I enjoy using watercolour and don’t use it a lot but there is always something you can learn by taking a class.

The thing which really struck me at this class was the students’ lack of knowledge and understanding about the paper they were using so I thought I would do a bit of research, add to the knowledge I already have, and try to break it down a bit for you. This is literally scratching the surface of what there is to know about watercolour paper but it is a start and I will write more about it at a later date.

Basically, there are three main types of watercolour paper: handmade, mould made, and machine made. Handmade paper tends to be made of 100% cotton, it is extremely durable and can generally withstand scrubbing and lifting off colour from the surface without damaging it. It does tend to be heavier than other watercolour paper and often (and most attractive to artists) it doesn’t need to be stretched.

Mould made papers are machine produced. A pulp mixture is pumped into a stainless-steel vat and a cylinder is placed into it. The mixture forms a web over the cylinder mould and that is then pressed to form the different surfaces desired.

Some of these cylinders have a deckle frame (a wooden frame or fence used in papermaking) on them to replicate handmade papers. The normal size for these cylinders is 260cm around the circumference of the cylinder by 130cm wide, although rolls of watercolour paper can also be produced using this cylinder method.

Amongst the attractions of this type of paper are its consistency and good durability (usually better than handmade papers) and the different surface textures produced by each cylinder.

Machine made papers, also called Fourdrinier (which means “flat wire machine”), are made via a process in which a constant stream of fibres and water are filtered out into a continuous loop allowing the formation of thin sheets of this wet mixture.

The mixture is then pressed to remove as much water as possible and then, still on the continuous loop, the sheets go through a drying machine. You will all have seen tv/movie footage of newspapers being printed and this paper is made in a very similar way using huge rollers passing through different areas to treat the paper giving a consistent finish.

The thickness of watercolour paper is indicated by its weight, measured either in grams per square metre (gsm) or pounds per ream (lb). The standard machine weights are 190 gsm (90 lb), 300 gsm (140 lb), 356 gsm (260 lb), and 638 gsm (300 lb). Paper weighing 356 gsm (260lb) or less really should be stretched to avoid “cockling”, where the paper wrinkles in areas with high water and paint coverage. During drying, the paint causes the paper fibres to swell. The paper deforms; it ripples and gets a wavy surface. Cockling can also occur when paper is stored in a humid environment.

The textures available for watercolour papers are:

Hot pressed, which is ideal for artists painting botanical works as the surface of the paper is completely smooth. As the name suggests, hot pressed paper is pressed between heated metal rollers to give its smooth finish.

Cold pressed, which is the classic, textured watercolour paper that you probably associate with watercolour pieces. It is the paper that most artists will probably use for their watercolour projects.

Rough surface paper, which is pressed between sheets of textured felt during the drying process. This paper is ideal for bold expressive mark making and not for intricate or detailed work.

Hot and cold pressed paper have the same surface texture, and this has a “tooth”, a term used to describe the surface feel. Generally, the more tooth a paper has, the rougher it feels. The lovely element to this paper is that paint will sink into the dimples of the paper which allows for a really interesting result if using paints which separate when used together.

So, what else do you need to know about paper? Traditionally watercolour paper is treated or “sized” using gelatin to stop the paint from sinking straight into the paper. The slight resistance gelatin allows means that the paint will sit on the surface and only partially sink into the paper.

Sizing improves the paper’s water resistance, decreases its ability to fuzz, reduces abrasiveness, and improves its surface bond strength. Paper can be sized internally (the gelatin is added to the mixture before pressing) or externally (the paper is soaked in a gelatin bath). High quality papers are both internally and externally sized and you can tell if a paper has excessive sizing if the paper resists the paint or it forms as ‘bubbles’ of colour that gather on the surface. Soaking the paper in water will remove excessive sizing. This will often be the result when you stretch paper which, as I said before, you really should if the paper weighs less than 356 gsm (260lb).

When preparing watercolour paper for stretching you may read or hear it suggested that you soak the paper in the bath for ten minutes before placing it on your board. Unless you have a dedicated bath or sink just for this purpose, I really do not recommend this as traces of soap, bubble bath, bath bombs or salts you normally use in the bath will probably still be present and they could contaminate your paper.

My advice is to gather your supplies together and first work with all the dry ingredients. Cut your lengths of gummed tape in readiness for placing on wet paper. Then take your paper and run it under a tap on both sides so that it is entirely wet. Place it on your board and then carefully run your tape under a slow tap. If you leave it under the water for too long the glue will wash away and nothing will stick and hold. I don’t sponge off the excess water as I don’t place the paper on the board too wet, having first allowed the water to run off. You will need to practice this, but you shouldn’t need to touch the paper at all.

Do make sure that your tape is long enough to fold over the paper and behind the board and make sure the tape is half on the paper and half on the board. If you don’t the paper and tape will fight each other and when everything is dry you could find that the three have separated from each other. Get it right and your paper will be held in place and be taut like the skin on a drum.

Nowadays you can buy watercolour paper in pad form which is gummed on all four sides with a small area at the top of the sheets which is not gummed so that you can easily slide a knife between the sheets to remove the paper from the other sheets on the pad.

Watercolour sheets traditionally come in the imperial size, which is 30” x 22” and depending on the method of manufacture there are two or four deckled edges.

Generally, you are advised to stretch paper sheets which are full imperial size although I admit that when using 638gsm (350lb) paper I do not stretch as I feel it is heavy enough for what I am painting on it.

If, however, your paper has been cut into half imperial or quarter imperial size then, depending on how much water you use, it may not be so necessary to stretch the paper if the weight of it is greater than 356 gsm (260lb). You will need to have a play and find out what works best for you.

There is a ton of other information about watercolour paper, the glues, size and manufacture depending on the brand you decide to work with but hopefully this is enough to get you going and may explain why some people on the class last week experienced problems with how their paper behaved when using the wet method being taught on the day.

NB all images were taken from the website https://www.art-is-fun.com where you can find additional information about watercolour paper. I do not benefit from advertising any of the products I feature in any of my blogs.

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