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Figuring Out Flash-Curing Parameters

(May 2006) posted on Tue Jun 13, 2006

Davis examines the variables to control when flash curing your garment prints and how artwork, mesh selection, and inks influence the flashing process.

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By Rick Davis

Table 1 Mesh Selection According to Ink Type

Ink type

Underbase mesh

Overprint mesh

High-opacity white

110-156 threads/in.

156-230 threads/in.

High-opacity colors

156-200 threads/in.

200-255 threads/in.

Transparent colors

110-156 threads/in.

156-230 threads/in.

Ink selection

Ink selection plays a crucial role. The underbase ink that you'll flash will set the printing conditions for the rest of the run. When flashing on dark garments, you want an underbase that has good opacity and good bleed resistance on synthetics, is fast flashing, and, most importantly, offers good after-flash characteristics.

There are some inks in our industry that are simply not intended to be flashed. Most notable are high-opacity fluorescents and metallics. These inks either have a lot of plasticizers (high-opacity fluorescents) or reflective properties (metallics) that resist the flashing process. Although these formulations are the exception and not the rule, you will still want to find the best white or color to employ as an underbase to allow for maximum productivity and minimal waste.

Flashing parameters

Once you've figured out which inks to flash and the meshes to use, your next challenge is to determine the actual flashing parameters. Based on your flash unit, these will include the distance of the unit to the garment surface, time the garment is under the unit, and the actual temperature setting of the unit itself. Many printers, especially those who use manual equipment, own flash units that do not have adjustable temperatures. If you own such a unit, your parameters are limited to time and distance.

The overall objective here is to flash the underbase with as little time and temperature as possible. Flashing hotter does not mean that you are necessarily flashing faster. You should be able to use a three- to five-second flash to make the surface of the underbase dry to the touch and not tacky.

One of the greatest mistakes made in this process is overcooking the underbase (at temperatures of 230-260ºF or higher). This results in poor intercoat adhesion. The underbase is cured, and the overprinted colors can't properly fuse during the curing process. When this happens, the overprint may separate from the underbase in just a few wash cycles. That's why you only want the underbase to reach 125-250ºF during the flashing process. You can use a non-contact pyrometer (temperature gun) to ensure that the proper temperatures are reached.

The guidelines presented here should help you develop effective flash-curing procedures in your shop. Each printing operation is different, however, so remember to test your procedures and document the settings you establish and the steps you take.


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