In part 1 of "What Emulsion Do I Need" we left you with fundamental information on the two types of screen printing emulsions. From the last blog you should now know that:
Pre-sensitized emulsion means that the emulsion does not require diazo, and is ready to use. This emulsion is less water resistant but has a longer shelf life and a tight exposure window.
Diazo based emulsion is going to be more water resistant but once you mix in the diazo, your shelf life becomes very short. You are also going to have a much wider exposure window.
Today we are going to discuss the following:
- When to use pre-sensitized emulsion and when to use diazo sensitized emulsion
- How long should emulsion dry before exposing
- How long to expose emulsion
1. Let's dive into when to use each emulsion:
Pre-sensitized Emulsion is going to be your best all around choice for textile printing and is the best emulsion to be used with plastisol inks. Most of the time the go-to ink choice for textiles is plastisol and that goes for both noobs and experienced printers. However, we are aware of times you may want to print with water-based inks and that is also possible with a ready to use emulsion that is water resistant. Ecotex® PWR Water Resistant Screen Printing Emulsion is a ready to use emulsion that handles plastisol ink and short run water based ink printing.
Two Part (diazo required) Emulsion: When you are going to print posters, stationary cards, or things of that nature these prints normally require higher detail and some sort of ink that can air dry. These prints are going to require water-based inks and a diazo based emulsion that can withstand the water that the inks contain.
2. How long should emulsion dry before exposure?
This is another popular question we get when it comes to emulsions. Both pre-sensitized emulsions and diazo emulsions need to be completely dry before exposure, how will you know? Touch it! If it has a slight tack to it, it's not ready yet. Now we can't tell you how long it should take because some people live in really hot dry climates, some live in really humid areas, some printers use drying cabinets with heating elements in them. There are so many variables that can be involved that all we can really say is it needs to be dry and we recommend drying overnight. Rushing this can result in the whole screen washing off.
3. Exposing emulsions
Now for the most asked question ever... how long should I expose my emulsion? This varies greatly between the two types of emulsions and the type of screen printing exposure unit used, along with a dozen other variables. Just remember your pre-sensitized emulsion is going to expose much quicker than your diazo based emulsion.
Here is a chart of our emulsions and the approximate drying time based on the light source. We are in dry weather with little humidity and are using the same light setup for each test. Please remember your results will vary!
Please take into consideration everything above is recommendation, except the emulsion being dry before exposing... that is law.
Further considerations
- We find that our TEX-Red Emulsion (ready to use) is the easiest to work with for beginners with DIY light set ups
- Our PWR Emulsion (ready to use) is an easier to use emulsion for a water resistant stencil, if you are printing with water-based inks
- Diazo based emulsions will work on almost any type of exposure unit because they naturally take longer to expose.
Still unsure of what you need? Take the emulsion quiz to find out.
Let's Talk
Remember, we are here to help! Drop a comment below or email our support team at info@screenprintdirect.com
