Ask the Expert: Can I Frame a Canvas Without Glass?

It's a common question we hear at HM Canvases, especially from artists transitioning between mediums or collectors acquiring their first painting: Do I need to put glass over my canvas painting?

The short answer is a definitive no. In fact, applying glass directly over a traditional oil or acrylic painting on canvas is usually discouraged. Unlike framing a photograph or a pastel drawing on paper, a painting on canvas is designed to stand on its own, with its protection coming from a completely different source: archival varnish.

Here's why canvas paintings are displayed without glass, and why that final layer of varnish is so crucial.

The Canvas is Built for Exposure

A professionally constructed canvas, such as those built with our stable Tulipwood stretcher bars, is inherently designed to be displayed without a protective glaze. This is thanks to the nature of the materials themselves:

• Medium Robustness: Oil and acrylic paints cure into solid, durable, and relatively stable films. Once dry, they are resistant to normal airborne contaminants and casual handling. They are not delicate powdered pigments, like pastels, which require a physical barrier to keep them from smearing or falling off the support.

• The Varnish Barrier: The true protective layer for a canvas painting is the final coat of archival picture varnish. This thin, transparent layer is applied after the paint is fully cured. It seals the entire painting, protecting the surface from:

  • UV Light: Minimising the effects of light-related fading.

  • Dust and Dirt: Sealing the microscopic texture of the paint surface.

  • Moisture: Providing a uniform barrier against humidity.

Crucially, modern archival varnishes are designed to be removable. This means that decades down the line, a conservator can safely remove the layer of accumulated dirt and aged varnish without ever touching the paint layer beneath, preserving the work for the next generation.

Why Glass and Canvas Don't Mix

Placing glass directly over a stretched canvas can introduce several problems that detract from the art and compromise its structure:

1. Loss of Aesthetic Appeal: Oil and acrylic paintings have texture, depth, and specific gloss levels (matte, satin, or gloss). Glass introduces a reflective surface that creates distracting glare, dulls the colours, and flattens the appearance of any texture (impasto).

2. Structural Interference: If the glass is fitted too tightly against the frame, it can restrict the canvas's natural movement. All canvases—even those on ultra-stable Tulipwood—slightly expand and contract with humidity changes. Restricting this movement can cause unnecessary tension or bowing.

3. No Breathing Room: Art materials need to "breathe." While the canvas surface is sealed by varnish, air circulation around the frame is important. A sealed, non-ventilated space (which can happen in a poorly fitted, large frame with glass) can trap moisture against the back of the canvas, encouraging mould or mildew growth.

When Glass is a Necessity vs. When Varnish is Sufficient

The need for glass is entirely dependent on the medium and the support.

Medium & Support	Protection Required	HM Canvases Solution
Oil/Acrylic on Canvas	Varnish only	Displayed without glass, often using a Tray Frame (Float Frame) to protect the edges.
Pastel/Charcoal on Paper	Physical Barrier	Requires glass and an acid-free mat/mount. The mat creates a vital air gap to prevent loose pigment from touching the glass.
Photo/Print on Paper	UV Protection	Requires glass (ideally UV-filtering) to prevent the paper and ink from fading and yellowing.

The Framing Solution: Beyond the Glaze

A Painting Framed with a Floating Tray Frame

Since your canvas doesn't require glass, the professional framing solution is often a Tray Frame (or float frame).

• Definition: The canvas sits inside a simple box-like frame with a small, uniform gap between the canvas edge and the frame's border.

• Purpose: The Tray Frame provides a crisp, finished edge and protects the canvas corners and sides from accidental bumps and scuffs during transport or hanging, all while allowing the artwork to be seen in its full, textured glory.

Invest in a quality archival varnish for your completed painting, and then choose a sturdy frame that supports and defines its structure. You can rest assured that your canvas is perfectly protected and ready to be viewed just as the artist intended—unfiltered and direct.