Surface Preparation: Sizing & Gesso

Summary

In this tutorial, Colin from Opus Art Supplies in Langley guides viewers through the process of preparing a raw canvas for painting. He emphasizes the importance of sizing the canvas to protect it from paint damage and decay, using modern products like Golden GAC 400 and GAC 100. Colin demonstrates how to apply these sizing agents and gesso, offering tips for both acrylic and oil painters to achieve a stable, long-lasting surface. He also discusses various options for gesso, including how to create different textures or smooth surfaces, ensuring the canvas enhances the final artwork.

Takeaways

• 😀 Sizing the canvas is crucial for protecting the fibers and ensuring longevity, preventing damage from moisture and paint absorption.
• 🎨 Golden GAC 400 is a recommended sizing agent, as it strengthens the canvas fabric and helps prevent support-induced discoloration in acrylics.
• 🖌️ Applying the sizing should be done with pressure to fully coat the fibers of the canvas, including the front, sides, and back.
• ⏳ Each coat of sizing should be left to dry for about 30 minutes to an hour before applying the next layer.
• 💡 For acrylics, adding two coats of Golden GAC 100 after the sizing is essential to prevent discoloration from water-based paint.
• 🔍 Sizing with PVA or GAC 400 helps prevent the paint film from cracking due to the expansion and contraction of traditional sizing like rabbit skin glue.
• 🖼️ When priming the canvas with gesso, start with the sides and back, then work your way to the front to avoid marring the surface.
• 🧴 Gesso is typically opaque white, which helps paint colors appear more vibrant on the surface.
• 🌟 The number of gesso coats depends on the desired finish: more layers provide a smoother and whiter surface, ideal for bright colors.
• 🛠️ You can control texture by adjusting the amount of gesso applied; more layers give a thicker texture, while fewer coats create a smoother finish.
• 🖍️ Gesso can be sanded between coats for a smooth surface or left as-is for a more textured effect, depending on the artist's preference.

Q & A

Why is sizing important for artists when preparing a canvas?

Sizing is crucial because it seals the canvas fibers and protects them from breaking down over time. It also ensures the longevity of the artwork by preventing the paint from penetrating the canvas material.

What are the traditional and modern alternatives to rabbit skin glue for sizing?

Traditionally, rabbit skin glue was used, but modern alternatives include Gamblin PVA size and Golden GAC 400. These alternatives are preferred because they are more stable and do not cause issues like the hygroscopic nature of rabbit skin glue, which absorbs moisture and can cause paint cracks.

What makes Golden GAC 400 a good choice for sizing a canvas?

Golden GAC 400 is a good choice for sizing because it stiffens the canvas slightly, making it ideal for acrylic painting. It also prevents support-induced discoloration, which can occur when water from acrylics soaks into the canvas and draws impurities through the paint layers.

How should you apply the sizing to ensure the canvas is properly treated?

You should apply the sizing using a wide nylon brush, making sure to scrub it into the canvas thoroughly. It’s important to cover the front, sides, and back of the canvas to protect all areas from deterioration over time.

Why is it important to apply pressure when brushing on the sizing?

Applying pressure ensures that the sizing fully coats the fibers of the canvas, which helps to seal them properly and provides better protection against the elements, preserving the integrity of the artwork over time.

How do you know when the sizing has dried enough for the next coat?

You can check if the sizing is dry by tapping it to see if it's tacky. If it's not tacky and feels cold, it indicates that it hasn't dried fully yet. Once it feels warm to the touch and dry, you can apply the next coat.

What is the role of gesso in canvas preparation?

Gesso is applied to create an absorbent surface for the paint. It acts as a primer, ensuring that the paint adheres well to the canvas. Gesso also helps to prevent any discoloration of the paint caused by the natural properties of the raw canvas.

What is the benefit of applying multiple coats of gesso?

Applying multiple coats of gesso helps to build up a smoother, whiter surface for the paint. The more coats applied, the smoother and more opaque the canvas will become, which allows the colors of the paint to appear more vibrant.

Can you create different textures by adjusting the number of gesso layers?

Yes, the more coats of gesso you apply, the heavier the texture can become. If you prefer a smooth surface, you can sand in between the coats. Alternatively, fewer layers will result in a more textured surface.

Is the canvas always white after applying gesso, or can it be customized?

While gesso is typically white, it can be customized. For example, you can use black gesso or tint clear gesso with fluid acrylics to start with a different tonal range, allowing artists to experiment with unique backgrounds and color schemes.