I use Panels, in my case thin plywood of either luan or sande plywood, 1/8" thick which are glued to 1 inch by 2 inch (3/4 inch by 1 1/2 inch actual) pine backing boards, The backing boards keep the plywood panels from warping and provide some protection for the edge of the painting.

There are several reasons I use this as my painting foundation :

The plywood is relatively strong, rigid and more permanent than canvas or linen. It may warp but only a very tiny bit. It will never need re-stretching, will not rot or be attacked by insects.

Canvas or linen will continually stretch over the years. That's what happens to a fabric that is tightly fastened to a wood frame. If you look at really old paintings or even some newer paintings on stretched fabric, you will see the painting "sags" from the corners. Re-stretching a canvas or linen painting is best done by a professional and it is not cheap.

Plywood provides a stable painting surface. What I mean here is that when I apply a paint brush to the plywood, the plywood does not "give". Canvas, no matter how tightly stretched, gives when a paint brush is applied. This makes it hard to apply detail accurately.

Plywood surfaces can be sanded and primed to my exact requirement. No matter how it is prepared, canvas or linen will always have a fabric "pattern". This can be difficult to work with when doing detailed work.

Plywood on the supporting frame does not need to be framed. When I do a trompe L'oeil, I don't want to add a frame since I have usually already added a frame within the painting itself. Some people prefer unframed pieces of art. Framing is expensive. But at the same time, my paintings on panel can be framed if desired.

Many people ask me why I don't use oil paints instead of acrylics. I'll go through each reason in detail:

Acrylics are more durable and reliable in the long run. "But wait! How can you say that when acrylics have only been around since the mid-20th Century?" Well, advanced scientific aging testing confirms this. Acrylics fully cure within a month or so, it depends on the temperature, humidity and how thick the paint coating is. This curing period is when the paint builds a tough, impenetrable barrier.

Oils take centuries to "cure". Gradually the oil in the paint - in most cases linseed oil - completely dries up, gradually shrinking the entire surface of oil paint on the substrate (canvas or wood in most cases.) How do you know an oil painting is old? It has cracks in the surface. These cracks may add a bit of character, but frankly, they distract from the overall painting.

Acrylics don't smell and they clean up with soap and water. I don't like the small of linseed oil based studios. And if you've ever seen a sink used by a oil painter to clean their equipment and brushes, they are a mess. You have to use solvents to clean up after painting with oils - that results in toxic waste. No thanks.

Acrylics dry to the touch quickly. Dry time is different from cure time. Drying time is when the paint is dry to the touch and the painting can safely be moved without fear of rubbing the paint. Acrylics generally dry to the touch within five minutes unless heavily applied. This doesn't change much unless it is really humid or really cold. Acrylics really shouldn't be used or cured below about 40 degrees F. But I'm not going to paint in a cold studio, so that's not a problem.

Oils on the other hand can take months to even dry to the touch. They are very sensitive to how much oil is used while painting as a thinning medium. Temperature and humidity can greatly effect drying time.