Some screen printing inks are labeled as “ready for use”, but that typically isn’t the case. While it is true that you can use the inks right out of the container, you may find a benefit in taking the extra step of prepping your ink before you start your next shirt run.
Plastisol is the most widely used screen printing ink. It is great for many reasons, especially its ease of use and ability to sit around without drying out in the bucket or the screen. Unfortunately, this creates lazy practices. Lazy practices then lead to failed runs from inconsistent ink coverage or curability. While you can leave your ink exposed in the shop, the risk is that dirt, dust and grime could end up in the ink. You may not be able to see it, but it will cause an uneven spread of ink on your screen and garments. Storing your ink is another factor. Be sure to store your ink at room temperature if you can help it. Curing in the bucket is not likely, but it can start the process around 90F. You will want to make sure you always stir your ink to ensure consistency.
If it has sat around for a long time, you can add a reducer to your ink. This reduces the viscosity of your inks. Many people use reducers to improve the hand-feel of their garments and allow for better printability. You don’t have to worry about changing the cure time when you add reducer. There is no limit to the amount of reducer that you can add to your inks; however, there are some guidelines that will help you get the most out of the product. For puff inks, you will want to add the reducer no more than 10% by weight otherwise it will reduce the puff height. Excessive amounts of reducer will also require an increase in cure temperature. Keep in mind that for every 5% of reducer added, the viscosity of your ink goes down by 25%. Additions above 10% may also lower the bleed resistance and opacity.