If you’ve ever watched your watercolor paper buckle the moment it gets wet, you know how frustrating it can be. Buckling—often called cockling—causes paint to flow into unwanted valleys, making smooth washes difficult and unpredictable. Stretching watercolor paper is one of the simplest ways to keep your surface flat from start to finish, and it can completely change the way you paint.
Why Stretch Watercolor Paper?
Any sheet lighter than 200lb, or about 425gsm, will naturally cockle when it becomes wet. As water is absorbed, the paper fibers swell, causing the sheet to ripple. These ripples create low points where paint pools and dries unevenly, often leaving unintended lines or blooms.
Stretching solves this problem by soaking the paper until it fully expands, securing it to a rigid surface, and allowing it to dry under tension. As the paper dries, it shrinks back to its original size and becomes taut, creating a smooth, stable surface that allows you to paint freely—without fighting the paper.
Materials You’ll Need:
Before you begin, gather the following supplies:
Watercolor paper (under 200lb benefits most from stretching)
A sturdy board that won’t warp when wet, such as a smooth wood panel or solid core board
A shallow tub, tray, or clean sink for soaking
A sponge
Clean water
A craft knife or utility knife for removal after painting
Step 1: Prepare Your Paper and Board
Start by cutting your watercolor paper about three centimeters larger on every side than your intended artwork. This extra margin will be covered by tape and later trimmed away.
Your board should also be at least three centimeters larger than the paper on all sides and strong enough to withstand tension without bending. Smooth wood panels or solid core boards work especially well for this purpose.
Step 2: Prepare the Gummed Tape
Cut strips of gummed paper tape slightly longer than each edge of your paper. Set them aside and keep them completely dry until you’re ready to apply them. Preparing the tape in advance makes the stretching process smoother and more controlled.
Step 3: Soak the Paper
Place your paper in clean water to soak. Most 140lb watercolor papers need about five to ten minutes, though soaking time can vary depending on the brand and composition.
You’ll know the paper is ready when it feels floppy—similar to wet cloth. At this stage, the fibers have absorbed all the water they need. Avoid soaking the paper for too long, as oversoaking can remove surface sizing and make the paper overly absorbent, causing paint to sink rather than sit on the surface.
Step 4: Position the Paper on the Board
Once the paper is fully soaked, lift it by one corner and allow excess water to drip off. Lightly dampen your board, then bring the paper to the surface.
Gently bow the paper in the center and lower it onto the board so the middle touches first. The sheet will naturally settle flat on its own. If it isn’t centered, simply lift it and try again.
Next, dampen your gummed tape using a lightly squeezed sponge—just enough to activate the adhesive without washing it away. Apply each strip so that half of the tape overlaps the paper and half adheres to the board. Smooth the tape gently with your fingers, being careful not to stretch it.
Step 5: Let the Paper Dry
Allow the stretched paper to dry completely, preferably overnight. Dry the board flat and avoid rushing the process. As the paper dries, it shrinks back to size, pulling evenly against the tape and creating a perfectly taut painting surface.
Removing Your Finished Painting
After your painting is complete and fully dry, remove it by cutting along the inside edge of the tape with a sharp knife. This leaves half of the tape on the border of the sheet.
Most artists leave this tape in place, as it will be hidden under a mat when framing. Removing gummed tape with water can risk damaging the artwork, and the taped edge adds extra stability.
Alternatives to Stretching
If you prefer not to stretch your paper, there are a few reliable alternatives:
Heavyweight watercolor paper (over 200lb) naturally resists cockling
Watercolor board, which is watercolor paper mounted to a rigid backing, stays flat even with heavy washes
Both options are excellent choices for artists who want a flat surface without the preparation time.
