Do you need to prepare watercolor paper at all?
Not always. Heavy paper, such as 300 lb (about 640 gsm), often stays flat without any preparation. Watercolor blocks, which are glued around the edges, are also designed to stay flat as the painting dries. Paper at 140 lb (300 gsm) behaves differently depending on how much water you use: light washes may be fine, while heavy, wet-in-wet work can cause visible ripples.
Lighter paper, such as 90 lb (about 190 gsm), usually benefits from stretching or at least taping down. If you are choosing paper, see the best watercolor paper for how weight and fiber affect this.
Why watercolor paper buckles
Paper is made of fibers that swell when they absorb water. When one area gets wet, it expands while the dry areas stay put, so the sheet ripples. As it dries it shrinks again and may not return to flat. Stretching works by wetting the entire sheet so it expands evenly, then fixing the edges so it dries tight and flat.
Basic preparation for any sheet
- Choose the working side. Many painters use the side where the watermark reads correctly, but either side is usually workable. Pick one and keep to it.
- Cut or tear to size. If you are cutting from a large sheet, a ruler and a sharp blade or a tearing edge both work. See standard watercolor sizes if you are deciding how to divide a sheet.
- Keep the surface clean. Oils from your hands can affect how paint takes. Handle the paper by the edges.
- Sketch lightly. Use a soft pencil and a light touch. Heavy lines can dent the paper, and hard erasing can roughen the surface. See how to draw for watercolor painting for light sketch methods.
What you need to stretch paper
- Watercolor paper
- A rigid, waterproof board, such as a sealed wood panel or a plastic-faced board, larger than your paper
- Water-activated gummed paper tape
- A tray, sink or bath large enough for the sheet
- A clean sponge or soft brush
- Clean water at room temperature or lukewarm
- A towel
How to stretch watercolor paper
- Cut the tape. Cut four strips, each a little longer than the side it will cover. Keep them dry until needed.
- Soak the paper. Submerge the sheet in clean water for a few minutes, until it is fully wet and relaxed. Many guides suggest roughly three to ten minutes, depending on weight; heavier paper needs longer.
- Drain. Lift the sheet by a corner and let excess water run off.
- Lay it on the board. Place it flat on the board and smooth it gently outward from the center with a sponge or clean hand to push out air bubbles.
- Wet the tape. Moisten the adhesive side of each strip with a damp sponge. Avoid soaking it, which washes the glue away.
- Tape the edges. Place each strip so about half is on the paper and half is on the board, then press firmly. Gummed tape works better than masking tape, which usually fails on wet paper.
- Dry flat. Leave the board lying flat at room temperature until the paper is completely dry. Avoid direct heat or a hair dryer, which can make it dry unevenly and tear against the tape.
Painting and removing the paper
When the paper is dry and taut, you can paint. It may ripple slightly while wet and tighten again as it dries. After the painting is dry, cut along the inside edge of the tape with a blade, taking care not to cut into the board. Any tape left on the paper can be trimmed away or hidden under a mat. See how to mount a watercolor painting for the next step.
Lighter alternatives to stretching
- Taping dry paper: Use artist tape or masking tape on dry paper to hold it on a board. This keeps edges in place and gives a clean white border, though the center can still ripple.
- Clips: Bulldog clips hold paper to a board quickly, but leave the edges unprotected.
- Blocks: Glued on all sides, so no stretching is needed. Slice a sheet off with a palette knife once dry.
- Heavier paper: The simplest solution, if the cost is acceptable. It matters most for large scale watercolor painting.
Troubleshooting
- Tape lifts as it dries: The board may be sealed poorly or dirty, or the tape was not pressed well. Wipe the board and use fresh tape.
- Paper tears at the tape: It dried too fast or was stretched on a surface that grabs it. Let it dry slowly and flat.
- Paper still ripples: You may have used light paper with too much water. Try heavier paper, or reduce the amount of water.
- Paper looks different after soaking: Soaking can reduce surface sizing slightly in some papers, which changes how paint flows. Test on a scrap piece first.
FAQ
How do you stretch watercolor paper before painting?
Soak it, lay it on a board, tape the edges with wet gummed tape, and let it dry flat.
Can you use watercolor paints on regular paper?
Yes, but thin paper buckles and may pill. Use light washes, or switch to paper made for watercolor if you want to work wet.
Should I wet the paper before painting too?
That is a different question, covered in should you wet watercolor paper first.