For some recent paintings, I used a piping technique to make fine lines of acrylic paint, as if I was icing a cake.
This technique should work with any acrylic paint. Because you will dilute the paint with a lot of gel, it’s better to choose a high-quality paint with lots of pigment, such as Golden Heavy Body Acrylics. I’ve come to prefer Golden Fluid Acrylics, tiny bottles of pigmented joy, which can be dropped into any gel or medium like food-colouring.
You will also need:
- Golden Heavy Gel, or Extra Heavy Gel (Matte or Gloss as desired)
- Small containers, 1 for mixing each colour
- Zipper bags, sandwich size, 1 for each colour
- Twist ties, 2 for each colour
- Paint brushes
- Palette knives
- Colour Shaper (silicone-tipped tool)
- Cellulose sponge, moistened
- Water, in a squeeze-bottle
- Canvas or other surface, with background already painted
- Scrap surface (cardboard, palette paper, etc.)
- If you’re using a heavy-body paint, mix up a small quantity of paint in the colour you want*, in a clean mixing container, using a brush, palette knife or Colour Shaper. Add 1-4 tablespoons of gel to your paint.
- If you’re using a very liquid paint, it’s easier to add drops of paint into 1-4 tablespoons of gel, to see the mixed colour.
- The gel:paint ratio could be anywhere from 2:1 to 10:1, depending on the strength of your pigment, the viscosity of your gel, and how stiff you want the paint “icing” to be. Add a few drops of water if you need to reduce viscosity.
- Mix the paint & gel very smoothly, but slowly to avoid air bubbles.
- Turn a zipper bag almost inside out, to expose one corner. Scoop the paint in with your brush or other mixing tool. Scrape and squish the paint icing into that corner, using a clean palette knife on the outside of the bag.
- Twist the zipper bag around your corner of icing, and apply a twist tie to keep the paint icing in place. Apply a second twist-tie to bundle up the rest of the bag into a handle.
- Cut a tiny corner off the bag. This cut determines the size and shape of your piped line. I aimed for 1 millimetre. Clean any paint off your scissors.
- Practice piping lines on a scrap surface. Cut the bag corner larger if required. To adjust colour or viscosity, you’ll need to scrape or squeeze the paint icing back into your mixing container.
- Pipe lines onto your prepared surface. Maintain an even pressure to get a smooth line. To make smooth curves, keep the bag tip touching your surface.
- If you make an error, remove the paint icing quickly with a sponge. A moistened Colour Shaper can adjust small bits of paint icing that stick up.
- Wait at least 1 hour for the lines to dry, since this paint icing is thicker than a layer of paint.
Advanced method that I have not tried: use a piping bag and tips designed for cake decorating. This would provide a well-controlled line width, and a variety of other tip shapes. However, you would need to clean out the equipment (quickly) between each colour.
* As you may know, acrylic gel is milky white when wet, but clear when dry. Because of that, and the usual darkening of acrylic as it dries, your wet paint icing will be significantly lighter in colour than your final dried lines.
Here is one of the resulting paintings: