Why do I need to stretch watercolour paper?

Paper absorbs water and expands unevenly, causing buckling and cockling. Stretching wets the paper fully, then holds it flat as it dries. When you paint on stretched paper, it stays flat because it cannot expand further.

Do I need to stretch heavy paper?

Paper of 300 gsm and above is less prone to buckling and many artists skip stretching. However, heavy washes on any weight can cause cockling. If in doubt, stretch it. 190 gsm paper should always be stretched.

What is the best stretching method?

Gummed tape (brown gumstrip) is the traditional method and works reliably. Stapling is faster but leaves holes. Clips and stretcher frames are reusable but may not hold heavy papers. For beginners, gummed tape is recommended.

How long should I soak the paper?

Lighter papers (190 gsm) need only 2 minutes. Standard 300 gsm needs about 5 minutes. Heavy 425-640 gsm needs 8-12 minutes. Over-soaking can damage the sizing. Soak in clean, cold water.

How long until I can paint on it?

The stretched paper must dry completely — typically 4-18 hours depending on weight and conditions. Do not use a hairdryer as uneven drying causes warping. Let it dry naturally, flat and horizontal.

ArtCalcs

Paper Stretch Calculator — Watercolour Paper Stretching

Calculate gummed tape length and soaking time for stretching watercolour paper.

Paper Width

Paper Height

Paper Weight

Stretch Method

How We Calculate This

How Paper Stretching Calculation Works

Tape length = Paper perimeter + Corner overlaps

The perimeter of the paper plus 50 mm overlap at each corner gives the gummed tape needed. Soak and drying times are based on paper weight — heavier papers need more time. The board should extend at least 20 mm beyond the paper on all sides.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify quantities before purchasing materials.