By Marion Boddy-Evans
The stiff but pliable, normal acrylic medium used in most of our paints and mediums is often too stiff for comfortable use on wearables. And, as any artist knows, once you get some acrylic paint on a fabric, it’s not going anywhere anytime soon. But as it gets laundered the aggressive action of a clothes washer and dryer, and shifts of cold to hot water, begin to cause cracking and flaking of the paint films.
Golden makes two heat-settable fabric additives, based upon the same binder: GAC 900 and the Silkscreen Fabric Gel. The much softer and more elastic GAC 900 blends with the durability of the harder paints and the balance tends to work quite well.
Normally a 1:1 combination is suggested for cotton or cotton/polyester fabrics, but when it comes to silk, most people want to retain the feel of the material, and this requires adjusting the ratio. Increasing the level of the GAC 900 to more of a 2:1 ratio produces a softer hand. (By the way, silk garments are commonly hand washed and air dried, which is what we would also suggest for the best wear of any painted garment.)
Another issue is film thickness. It is imperative when trying to retain the feel of the silk to keep the paint films very thin and stain-like. This is not a problem when using Fluid Acrylics and GAC 900 as they result in a pretty thin mixture.
Avoid building up multiple coats in any given area as well. Because of this, using Silk Screen Fabric Gel should be limited to use for its intended screening purpose on silk and not used for brush applications which may otherwise be fine on a cotton garment.
Heat Setting Paint on Silk
GAC 900 mixtures tend to be very tacky after air drying, and less after heat setting. The temperature and time of the heat setting process is a variable sliding scale. If the fabric can withstand hotter temperatures, then heat-setting is done at a higher temperature and for a short time, usually mere seconds when using a commercial heat setting press. However, the home user is more limited to a standard clothes iron or clothes drier, and the lower temperatures mean more time to achieve a proper heat setting.
When working on silk, it is imperative to follow the industry standard guidelines for how to properly iron it, as things like excessive heat and pressure on the fabric can damage the material. Going back to the sliding scale idea, it means use the low setting for a bit of time, probably into the range of 20 or more minutes per garment, which is why the preferred method is to use the clothes drier with a low setting so that several items can be laundered at once and without the pressure of an iron.
— Michael S. Townsend