Chapter 17
Curing Plastisol Inks On Printed Garments
Being sure your plastisol ink is wash safe and can endure through many washings is critical. Plastisol ink is a type of ink used for screen printing textiles. Plastisol inks are the most common inks for printing designs on garments, and are particularly useful for printing opaque graphics onto dark fabrics. Plastisol inks are not water-soluble. Because the ink is made up of PVC particles suspended in a plasticizing emulsion, the ink will not dry if left for extended periods of time. Plastisol inks are recommended for printing on colored fabric and on lighter fabric; plastisol is extremely opaque and can retain a bright image for many years. Plastisol inks will not dry, and need to be cured as a result. Curing the inks can be done with a flash dryer, or a belt oven. Most plastisol inks need to reach a temperature of about 330 degrees Fahrenheit before being fully cured. Plastisol tends to sit on top of the threads instead of soaking into them, giving the print a raised, plasticized texture. When printed through higher mesh counts, plastisol inks can produce a softer feel.
Under cured ink can wash out and over cured ink can prematurely flake off and crack. For about $30 to $40 you can buy a temp gun with a laser sight. Point the laser sight at the ink on the shirt as it is still 4 to 6 inches still inside the oven chamber and take a reading. It should have reached your optimum temperature for your brand of ink, typically between 320 to 340 degrees Fahrenheit. Check with your ink vendor on this.
There are many belt dryers on the market today. Make sure not to over purchase or under buy your dryer. Belt dryers have certain maximum rates at which they can run shirts through the chamber and reach optimum temperature. A dryer made for manual printing will not be able to keep up with an automatic press and you certainly do not need a dryer rated for an automatic press unless you plan on going automatic one day. Your dryer is yet another piece of equipment that you should purchase with your business goals in mind.
VIDEO: Tips On Curing Plastisol Inks
VIDEO: Curing Plastisol Inks In High Humidity Tips
VIDEO: How Do I Set My Infrared Belt Dryer?
VIDEO: How To Vent Your Belt Or Conveyor Dryer
VIDEO: How To Track The Belt On Your Conveyor Dryer
VIDEO: Curing Tests For Plastisol Textile Inks
VIDEO: How Long Does It Take To Cure Plastisol Inks?
Screen Printing With A Flash Cure: Advice On Flashing Tee Shirts
Using a flash cure unit to simply flash cure between colors in screenprinting is challenging enough but it is even more difficult when you are using your flash cure unit to complete the final curing of plastisol inks printed on tee shirts. Here are some quick tips for dealing with flash cure units.
Make sure to understand your flash cure unit. They can use infrared panels or quartz bulbs to produce the heat used to cure plastisol inks and they will perform differently based on their specifications. This is most critical with quartz flash units as the bulbs may be of different spectrum and therefore perform differently when curing light or dark inks. Some quartz flash cure units are specifically designed to flash cure white inks only. Infrared units are probably going to be easier to use for the beginner.
The distance between the flash cure unit and the tee shirt on the pallet will be the determining factor in flash speed. Even if your flash cure unit has a thermostat, it is very important to get the distance of the unit to the pallet correct for the dwell time you want to work with. That means if you are a slow shirt loader and printer, your flash cure unit will probably be a little higher off the pallet allowing you more time to complete your part of the cycle. The closer the unit is to the pallet, the faster the flash cure will be and it also increases the risk of scorching or burning.
It will help a lot if your flash cure unit is level and parallel to the tee shirt pallet. This will ensure consistent curing and reduce the possibility of scorching or burning at one edge or another. In the same respect make sure your garment is loaded properly and does not have any high points that will come in contact with or even just be closer to the flash cure unit. High points in the garment during flash curing will result in scorching or complete burning of the fabric.
Infrared flash cure units take some time to heat up much like an infrared oven dryer. It is a good idea to allow the unit to heat up prior to printing. It will also take some time for your pallets to build up some heat during printing and as they do, your flash times may be reduced noticeably. Remember, you do not want them to heat up too much because it will affect printing and possibly damage the pallet.
Wind or breezes of any kind near the flash cure unit may adversely affect the curing. Make sure there are no fans, coolers or window breezes near the flash station that will prevent the ink from curing properly.
It is best to try to get in the habit of swinging the flash cure unit's head away from pallets when you are not printing. Distractions during printing while using a flash cure unit may result in ruined product or damaged equipment. Wooden and press-board pallets will warp and burn under excessive flash cure heat.
Overheating any type of pallet adhesive will cause the adhesive to become gooey and it will not perform properly. It may even cause the adhesive to be pulled off with the garment and result in a sticky, tacky layer on the inside of the shirt. This will most often wash out on the first wash in the laundry but it is an eyesore to the customer and requires an unnecessary explanation.
When printing a multi color job especially on a white under base, make sure you give the ink enough time to cool between flash curing. Many inks like high opacity formulas may tend to stick to the back of another screen as you print the next color. Having cool down stations on a manual rotary tee shirt press will eliminate this problem.
Finally, if you are using a flash cure unit to complete the final cure of your printed garment, you would be well advised to have a temperature meter or "gun". Using a flash cure unit to cure larger print areas may be inconsistent. Using a temperature gun to verify your curing temperature of at least 320 degrees Fahrenheit will ensure you product will not wash out due to insufficient curing. A belt oven to cure screen printed garments is best and will provide the most consistent and reliable results. If you are planning to print any volume of tee shirts, a belt dryer is recommended.
Using A Flash Cure Unit To Do Your Final Cure
When first starting out in screen printing tee shirts for fun or for profit many people shy away from the higher costs of belt dryers to keep startup costs down. This is very understandable and sometimes even the space available may affect this decision greatly. Also, many people know that a flash cure unit can easily run on standard household electrical outlets meaning there are no extra costs in setting up 220 power for a belt dryer. Therefore, the topic of using the flash cure unit for the final cure is a popular topic of discussion among new screen printers. But doing so can make or break you if you do not understand how using the flash cure unit can affect your cure.
It is possible to use a flash cure unit to fully cure plastisol inks printed on tee shirts or other garments. But the real issue here is the consistency and the production rates of such a curing process. It is true that any heat source that can raise the temperature of the entire printed plastisol ink layer to around 330 degrees Fahrenheit will cure the ink. The problem with using a small flash cure unit or other small heat generating device is that it is almost impossible to ensure that every part of the printed design will get the same heat for the same duration of time. This problem may be greatly exaggerated when dealing with an order of hundreds of garments.
A common problem encountered when using the flash cure for the final cure is uneven curing especially around the edges. Often the heating elements in less costly flash cure units do not disperse the heat evenly. This causes parts of the design to be fully cured while other areas are not. The edges of larger designs can be especially difficult to evenly cure with a flash unit. When the garment is washed only certain parts or areas of the design will begin to wash out while other areas may be fine.
With an open heating element such as a flash cure unit, things like drafts, fans or any subtle breezes in the shop may affect the cure. The pallet board itself may reflect different amounts of heat radiation from area to area. You would be surprised at how a little variable in the shop can adversely affect your final cure. Even humidity can be a factor when curing 100% cotton garments. Shirts cured with flash cure units may often have wash out problems in certain areas of the print. I do not mean to make you think you cannot do it at all; rather it is impossible to do consistently and efficiently.
It will slow down your production rate drastically. Having to flash cure each shirt individually to finish the final cure is time consuming and takes up more space than you would think when handling the garments. A textile belt oven will solve these issues by providing a consistent curing process while speeding up production. The oven chamber provides for a more stable heating environment and the conveyor belt provides repeatable consistency at an acceptable production rate. I always recommend eliminating any variables in your screen printing process whenever you can.
Using a belt oven will reduce the variables in the curing process to an acceptable minimum. Remember, when working with plastisol inks, the final cure is critical. The last thing you want is a customer to come back to your shop with shirts that are washing out. Even worse, you do not want the customer to be wearing shirts that have washed out partially and telling everyone who printed them. Whenever possible, make sure to get the right tools for the job and it will save you a lot of time and money in the long run. Not to mention considerable heartache.
VIDEO: Can A Flash Unit Cure Plastisol Inks?
VIDEO: Setting Up & Using The Flash Cure Unit
VIDEO: Can A Heat Gun Cure Plastisol Inks?
VIDEO: Can A Heat Press Cure Plastisol Inks?
VIDEO: Can You Print Plastisol Ink On Laundered/Used Garments?
I will mention water-based inks are technically heat set rather than cured although you may here it referred to in that manner. Water based inks can also be manufacturer specific as far as the heat setting process and will usually require a forced air flash cure or belt dyer.