Flash dryers are a popular way to "partially cure" a screenprinted item before applying a second layer of ink. You can also use a flash dryer to fully cure a shirt, although conveyor dryers are more common. While not recommended for commercial or professional endeavours, homemade flash dryers can be a cheap way for amateurs to dabble in multilayer screenprinting. For DIY die-hards making smaller batches of shirts, this is as independent as screenprinting gets.
Build a five-sided wooden box to your specifications using the five pieces of untreated wood. The size depends on how large the prints are that you will be making. A typical size of each side is 12-by-12 inches. Make the box by nailing two sides to the outside edge of a third side. You will have a three-sided U-shaped object. Take your fourth piece of wood, insert it into the open side, and nail or drill both sides together. Then, attach your fifth piece of wood with nails or a drill to the top of this four-sided box. This box will be positioned, open side down, over the area where you cure your T-shirt.
Attach the four 2-by-4 pieces as legs along two facing sides of the box with nails or a drill and screws. They allow the box to stand, almost like stilts. You will be placing your screen-printed items underneath the open box on stilts.
Drill a hole large enough to fit a cord through in the centre of the top of the box. Insert your cord through the hole and install the four sockets for the infrared lights in the four corners of your box. You can install the bulbs by attaching sockets (do not use plastic sockets or glue), or you may use a staple gun to hold the cords in their corners and allow the bulbs to hang. The bulbs should hang at least 2 inches away from the work surface where you'll place your shirt. Attach the switch to the top of the box.
Insert your infrared bulbs into their sockets. Flick them on and wait five minutes. Wearing gloves, slide your freshly screenprinted T-shirt under the box on stilts until the temperature reaches 160 degrees Celsius (for plastisol ink) to be partially cured. Use an infrared temperature gun to measure how hot the shirt is.
DIY flash dryers do not produce the same professionally cured effect as a manufacturer's flash dryer, but are a good way for beginners to learn about the screenprinting process.
Be very careful with the temperature of the wood and bulbs on your flash dryer. It is a fire and burn hazard and must be monitored very closely. Store your flash dryer in a clean, dry work station away from clutter. Wait several hours after use to clean table or pallets used below your flash dryer.