Through a Glass Lushly: Michalina Janoszanka's Reverse Paintings (Ca. 1920s)

I paint on canvas, and the main reason I can think of is that there's no prep work to be done. You just apply oil to glass and done. With modern oil painting, you usually buy stretched, prepped, framed canvases that are ready for use straight away, but in this lady's time or before it, it was more common to use raw canvas and do your own surface prepping, cutting and framing, meaning gesso prep and stretching it across the frame for just the right level of tautness, which isn't something you do by hand, but with a special tool. All told, a more complex, time consuming and pricey process than just laying paint directly onto cut, hard glass.

Advantages

  - Its a transparent canvas

    - Works great for copying, if starting from a detailed work (line art, complicated writing) easier to reproduce all the tiny details.

    - The finished art can be transparent, translucent and incorporate index of refraction effects

    - It can be layered and use either further glass layers, traditional canvas as a backdrop, or be shown in a way that exposes the scene behind. [1]

     [1] https://www.artsyshark.com/2020/11/26/featured-artist-michael-frank-peterson/

    - It can be easily backlit / sidelit

  - It allows focusing on details if the art being produced is very detailed or line art in style

  - It can often convey depth easier because of the translucent quality of the thick layers of paint

  - Some pigments adhere better to glass than to traditional canvas, allowing other colors and mixtures normally difficult with canvas

  - Techniques normally not available, like flowing, dripping, runny water (that would normally be absorbed) can be used. [2]

    [2] https://iranian.com/Arts/1999/September/Azima/waterfall.html

  - The reverse layering often makes foreground features standout and be "crisp" as they completely dry and there's very little chance of smears or blending [3]

  - Techniques like using black additions behind colors to intensify them or increase contrast are available [3]

    [3] https://upload.wikimedia.org/wikipedia/en/f/f2/QingDynastyArtist-LargePartyatThrone.jpg

  - The finished art can easily be used for windows, portals, dividers, and other areas normally meant to be transparent (fishtank walls)

  - It can be adapted to almost any material that's transparent (plastics, colored glass, consumer objects)

  - Details need to done first

    - Means you need to have a really good idea of what you want to paint beforehand

    - You can't miss any details, because otherwise you'll have scrape away large areas of paint to correct

    - Can often take a long time checking and re-checking to make sure you didn't miss anybody's eyebrows or other tiny features

    - You can't change your plans midstream, or improvise very easily

      - Or the changes / improvisation need to mostly affect the background objects

  - Its transparent glass (or it's not traditional canvas)

    - Many of the art supplies and paint don't work the same (or even at all)

      - Ex: Watercolors don't get absorbed and diffuse

    - Several traditional art materials need additional adhesive layers to make them actually attach to glass

    - Techniques available on canvas may not be available or have to be completely redesigned

    - The painting surface itself is usually fragile, and significant risk of breakage / damage

  - It's often historically been stigmatized (viewed as an art style of primitives, religious people, or "feminine")