Vignette 3: About Watercolor Paper
Last updated 13 September 2020.
Watercolor paper is sold in different weights (grams per square meter or gsm; or alternatively, lbs per ream) and in three grades: hot pressed, cold pressed (also called not in the U.K., meaning not hot pressed), and rough. Cold pressed paper is pressed under cold weights rather than hot ones and so it has a rougher texture, which I recommend for beginning watercolorists. Rough press is unpressed and is rougher still. Rough press pulls lots of pigment from the brush making for intense colors (Vernon Washington uses rough paper for his animal portraits for this purpose.) But cold pressed is rough enough for me. I prefer paper that is at least 300 gsm (140 lb). 600 gsm (280 lb) has a bit more resistance to buckling and rippling, but I find that if the paper is properly stretched, 300 gsm works fine and it is half the price. You may have noticed that the weight of paper may be specified in two different units: gsm (metric system) or lbs (Imperial or British system). The metric (gsm) measure is more precise than the Imperial system. In the Imperial system, the weight of paper is given in lbs per ream (500 full sheets) of paper. Though typically 300 gsm = 140 lb, because the size of the sheet is unspecified, different manufacturers using different standard pages may differ in their assessment of paper weight. So, my advice is to make decisions with paper weight measured in gsm.
For beginners, I prefer cold pressed over hot pressed paper for a couple of reasons.
First, and this is counter-intuitive, but the smooth surface of hot pressed paper allows granulating pigments to move around more and clump together, resulting in a grainier appearance. For texture and background effects, this can be desirable, but often it is unexpected. If you choose to use hot press paper try mostly staining non-granulating pigments. Also beware of multiple applications of thin washes, which tend to concentrate pigment at the water's edge, although, hard edges are hardly fatal. After they are dry one may simply soften them with a wet brush and pick up the excess water with a little blotting. On the other hand, cold press paper has a rougher texture, but the painted features may appear smoother because the pigment doesn’t migrate as much, and since the pigment tends to settle more deeply into the mat, glazes are often more successful. (A glaze is an application of one pigment over another layer that has already dried. Usually, the underlying layer is a staining color because staining pigments tend to stay put rather than lift, and it is best to apply the glaze with a single stroke or two to keep the disturbance to a minimum. Thinner glazes may cause more lifting than thinner glazes, so it's better to practice on scrap paper until you gain competence.)
Second, Since the pigment tends to stay on the surface of hot press paper, paint lifts more easily. This can be good for some effects like lightening and blending skin tones, but it makes it more difficult to layer colors, especially glazes over granulating colors. Some artists nonetheless prefer hot press paper and use particular techniques to tame it. I now use hot press paper all the time, but, I think cold pressed paper is better to start with and a less frustrating way to build your watercolor skill.
I like Arches paper (pronounced "arsh" -- it's French) and typically use 300 gsm cold pressed, 100% cotton either in blocks or cut from a roll. Arches also makes a 280 gsm paper available in roll form (Arches En-Tout Cas -- a fancy way of saying "all purpose") which I do NOT recommend. It has the advantage of having one hot pressed side and one cold pressed side, however, Arches lists only 25% cotton on its label and will not say what comprises the other 75% of the paper. I do not like those kinds of shenanigans – companies should be above board about what is in their paper. Be that as it may, their 100% cotton product is quite good. Arches paper is available in sheet, roll, or block form with large rolls being the least expensive on weight basis and blocks being the most expensive. Rolls and sheets are necessarily un-stretched. Block papers are pre-stretched and hold the paper in tension with a plastic binder at all four edges except at a particular spot that is wide enough to insert a pallet knife. After the painting is complete and fully dry, one inserts a pallet knife between the top and next sheets and slides the pallet knife around the perimeter to cut through the binder. This frees the painting and exposes the next sheet.
Tip: when you come to a corner of the block, slide the knife point first through the binder on the adjacent edge, then continue forward to the corner. Cutting the adjacent edge before cutting the corner will keep you from tearing a sheet at the corner which is bound more strongly by the nexus of two fastened edges. Here the artist is removing the black protective cover to expose the white paper under it.
Why must watercolor paper be stretched before painting?
When watercolor is added to paper, the water is absorbed into the paper fiber by capillary action increasing the paper's internal pressure. The paper moves to relieve the stress and this creates hills and valleys on the painting surface (i.e., ripples). The watercolor pigment then tends to settle in the valleys rather than where you place it, causing irregular pigment deposition that is difficult or impossible to correct.
I recommend beginning with cold press paper pre-stretched in small blocks such as 7"x10" (actually the paper is 18cm x 26cm which equates to 7.09" x 10.25”). As for a price comparison, small blocks are about 80% more than large rolls, but by the time you account for the gum overlap and tolerance margins that you need for paper cut from a roll, the cost difference is not as great as one might think. (Some artists paint on unstretched paper, but I prefer that my paper remain flat.) Block paper in 7"x10" runs about a dollar a sheet for 300 gsm and is sold in 20 sheet blocks. This is a ridiculous size for a watercolor but that's what they make (wouldn't 8"x10" make more sense?), but if you are just beginning, you are going to need a lot of practice and you probably won't be framing it. At a dollar a sheet, you don’t have to feel guilty when you spoil a page as you will certainly do as a beginner (and really must do in order to grow as a watercolorist). Even if you spoil a page you can use the other side for scrap or additional practice, and smaller sizes undergo less rippling. All of my early artwork was done with block paper.
That being said, I find blocks to be inferior to paper that I stretch myself for larger sizes. In all but the smallest sizes, ripples are a problem. For blocks above 10” x 14” I find the ripples debilitating. When one pulls paper from a roll and stretches it properly, there are virtually no ripples or buckling, one is not stuck with weird paper sizes, and one can do very large works in sizes that are not available any other way. For large paintings, roll paper is less expensive than block paper, even after adjusting for gum overlap, borders, and tolerance (see Calculating Paper Size Dimensions below).
If you are interested in using roll paper, try a 51" x 10 yd roll of Arches 356 gsm (156 lb) 100% cotton cold-pressed paper for about $175. You can also get this in hot-press if you are so inclined. I also recommend using disposable cotton gloves to keep the oils from your fingers away from the paper and a large (60") Kraft Paper Roll Holder. I bought mine at ULINE.com for about $100. By the way, rolled paper has a lot of curl. A large paper roll holder will make it a LOT less frustrating to handle rolled paper without creasing.
Many Kraft paper roll holders are have "cutters," but these are little more than a straight edge and will not cut watercolor paper which is many times stronger than Kraft paper. To cut the paper from the roll I first use a pencil to mark a horizontal line and then cut it from the held roll with scissors or a box knife. If you are having issues with the curl, or you have inadvertently creased the paper, you may cut a length and throw it into a clean bathtub containing a few inches of cold water for five minutes. This will relax the curl and smooth out the creases. Then pull the wet paper from the tub, let the surface water drain off, and lay it on a flat waterproof surface to dry overnight. Paper dried in this way will have ripples, but the curl and creases will be gone and it can at least be cut and shaped without having to fight the curl. I use a mat cutter to trim the paper to square but you can just as well mark with a ruler and cut with scissors. Once I get a sheet to its desired dimensions, I stretch it to that it will remain ripple free when I paint. (See How to Stretch Paper below).
Calculating Paper Size Dimensions With Rolled Paper
Typically, you will add 2" to 5" to the desired Painting Surface Size whenever you cut paper from a roll, depending on whether you want to start from perfectly squared paper, how much of a border you want for matting, and to allow for gummed tape to be attached to the paper. So there are four sizes to keep in mind.
Painting Surface Size (innermost) — the area you intend to paint. It does not include any border.
Final Cut Size is the paint surface plus any border you intend to preserve once you cut the paper from the gummed tape.
Gum Size (includes additional area to accommodate the overlap of the gummed tape, staples, or both).
Rough Cut Size (outermost) — includes an additional trim tolerance to allow for trimming to square).
With these sizes in mind, three additions are required to the Painting Surface Size to arrive at a Rough Cut Size:
Rough Cut Adjustment (Optional, +1”). This is an adder to the paper to account for the fact that a rough cut from a roll is unlikely to be perfectly "in square". You will do your best, but adding an inch to the length and width of the final size is a good way to be sure you will have ample margin to trim the paper. You will trim the rough cut to the Gum Size in preparation for taping.
Gum Overlap Adjustment (Essential, +2”). This allows a 1” overlap of the gummed tape on all sides of the paper so that you can attach half of the 2"-wide gummed tape to your paper with an inch overlap to your stretcher board. Gottsegen recommends pushpins or thumbtacks to anchor the stretch, in which case you do not need gummed tape or much of an overlap adjustment and you can preserve the deckled edges if you like (see page 295 of his book). Nathan Selikoff has a method to simulate deckled edges even from cut sides of the paper.
Border Adjustment (1” to 2", optional). This optional adjustment adds a 1/2" to 1" border. Even though the border may be hidden by the mat, I prefer to have one rather than painting right up to the paper’s edge. This assures me that the matting will not cover any of my intended picture and that I can freely swing my brush outside the painted surface before lifting or reversing course. I use drafting tape to preserve the border because it will not loosen when irrigated by the water and pigment and is easier to remove than regular masking tape. I prefer not to paint on top of the gummed tape as the water may loosen the tape and allow pigment to run along or under it, or it may allow the gummed adhesive to migrate under the picture which will cause difficulty when removing it from the stretcher board later.
Example: you wish to have an 8 x 10 final painting surface size with a 1” border around it. What size should the Rough Cut be?
Answer: A one inch (1”) border requires a +2” adjustment from the Painting Surface Size because there are two borders in each direction. Thus, an 8”x10" Painting Surface Size requires a 10"x12” area to accommodate a one inch border. Another 2” must be added for a 1" gum overlap on all sizes, increasing the required surface size to 12”x14". Finally, I prefer to add a rough cut tolerance of 1”. This will provide for ½” of slop to all the sides to account for a rough cut from the roll that is not precisely square and an allowance to trim any deckled edges you may wish to remove. Thus the rough cut size should be 13”x15”. That is, 5” has been added to the length and width of the desired painting surface to arrive at the Rough Cut Size to pull from the roll. If you do not need a border only 3" needs to be added. If you can live with an off-square cut (which will just go under the tape) you only need 2" additional on each side.
How to Stretch Paper
Cut the desired size from the roll. I use disposable cotton gloves when handling the paper here to keep oil from my hands from getting on the painting surface. This is probably overkill, but I don't want the absorption of water to be hindered in places where I've handled the paper. I get my gloves from Amazon.com but they are cheap and available lots of places. For loose sheet paper, you will start with whatever size you have, but of course, your available painting surface will be smaller in length and width than your sheet size.
Inscribe the sheet with a 1” border using a pencil. (Don’t use pen, because even “permanent" ink bleeds when wet.)
Soak the sheet in cold water for 5 minutes or so, until a bent corner wants to stay bent rather than wanting to spring back. Weighted placement of the paper in 2" of water in a tub works well.
Remove the paper from the tub by holding it outside the border and allow the surface water to run off.
Lay the wet paper on a stretcher board. Any hard portable surface may be used as a stretcher board. This includes a wood or plywood board, but if you use wood, first spray it with workable fixative that has been allowed to dry overnight. I prefer large ceramic tiles (18" x 18"), or even flat tempered glass. Neither of these requires any pretreatment. Lately, I have been using some inexpensive 18” x 24” flat mirrors I found at Home Depot to anchor the stretch.
Sponge or lightly squeegee off the excess water.
Secure the paper to the stretcher board with 2"-wide Kraft gummed tape, lightly wetted to activate the glue. Let 1" of tape overlap the paper up to the border, leaving 1" to adhere to the stretcher board. Be judicious with the water. If you use too much, the glue will migrate under the paper, making it difficult to remove the paper from the board, or the tape will give up its hold and the stretch will fail. For this reason, some artists prefer to use a wooden board and not only tape the paper, but also use a staple gun to pierce through the tape and paper into the board as an extra measure of security. Any rippling at the staples tends to work itself out as the paper dries.
Go over the top of the tape with a damp sponge to assure that the tape is pressed against the paper and stretcher board all the way around the perimeter.
Let dry overnight. Hopefully, the paper has not pulled away from the tape. The border pencil line will let you know. If you see the border pencil pulled away from the gum tape and into the painting surface by ¼” or more, then you know the stretch has failed there. If it is fairly localized, you may chance it, or if an entire side has failed, you may cut the paper free per Step 10 and start over being careful not to over-wet the gummed tape; however, in the latter case you have lost the gum overlap and your paper is now 2” shorter in length and width. If the stretch has held, you are now ready to paint. Once the painting is complete and has completely dried (overnight), proceed to Step 10.
Cut the painting from the stretcher board using a utility knife alongside a safe cut rule. Safe cut rulers are very sturdy rulers with a built in hand guard and a rubber base that will not slide around as you cut. They are a worthy investment.
