Methods of screen printing
Stop!Don’t put this article down just because you a few years of experience. I teach beginners who can print better with ten minutes of instruction than many printers with years of experience. This article is written with the beginner in mind but take a few minutes – read this short article – and maybe there will be a tip or two to make even an experienced printer better. Why not.
Where Do You Start
The time has arrived. You just spent $15, 000 on equipment and you have made a s screen. Now what do you do? What if you ruin a shirt? What if the ink washes off? What if the customer isn’t happy? What if you put the print in the wrong location? Maybe this wasn’t the business you wanted after all. Traumatic, isn’t it!
Fortunately, you’ll get over it – but these are the questions and problems that face beginning printers.
This article is about some basic fundamentals of making a print. These are things that beginners AND experienced printers need to know. Make sure your existing printers read this article. How many times has a printer told you how many years he has only to not be able to produce a salable shirt. Just because they have the title “screen printer” doesn’t mean they are one!
For the purpose of this article we will assume you have a screen made using the correct mesh. No, 110 (43cm) monofilament doesn’t work for every job. You need to use the correct mesh count to have a good print. Although mesh count is an entire topic, for now let’s assume you are doing a simple three-color print on a light shirt. I would use a 160 (61cm) to 180 (70cm) monofilament mesh with either very well made wood frames that have been purchased with the fabric already attached (prestretched) OR I would use a metal retentionable screen that I had brought to the proper tension a couple of times to get the fabric very tight. I choose the 160 to 180 because I want to lay down a little less ink since this is a multi-color job AND in doing so I will not have to flash cure between colors. In fact I can print this job wet-ink-on-wet-ink. Trust me!
I would also have used a dual-cure photo polymer emulsion as my stencil since they can be used with only a single coat on each side and they hold up well, yet reclaim easily.
Square the Screen to the Shirtboard The screen needs to be placed on the press and squared to the shirtboard. This is as simple as placing a t-square under the frame and looking through the screen to square the image on the frame to the edge of the board. Now when you make a print it will be straight to the board.
Multi-Color Print Sequence
When printing multi-color prints on light shirts you generally print the lightest color to darkest color OR the smallest print area to the largest area. This sequence, along with the right ink viscosity will help minimize ink picking up on the screen bottoms. This is called build-up and is a common problem in multi-color printing. The easiest way to line-up screens on a multi-color print is to make a print of the outline or main color and just line-up the other screens to the print. Sure you may get a little ink on the bottom of the screen but guess what? It will wipe right off.
Adjust the Off-Contact Distance
The screen MUST be set to sit slightly off the shirtboard. This is called off-contact printing and is how all good printing is done. Some presses have adjustments for this. Others will need to have the screen shimmed from underneath. Either way, you may need to put a thin piece of cardboard under the edge of the frame so it will hit the shirtboard as the screen comes down. This may seem unorthodox, but again, trust me. You need to keep the screen from 1/16″ to 1/8″ off the shirt and no matter how well made a manual press is, the tip of the screen is going to move downward when you get to the end of the stroke and nothing is going to keep it off the board but a simple shim.
This is one area where there is a lot of confusion. The ink manufacturer told you that the stuff in the can was “Ready for Use” (RFU). That means just slop it in the screen and “pump up” to make a print. RFU is one of the greatest lies ever told.
Don’t Be Afraid of Additives
Most ink on the market it a little too thick to print easily by hand. It generally needs a slight amount of reduction – thinning – to make it work better. Thinning does not mean making it softer so I am talking about adding a curable reducer rather than a “soft hand” additive. A small amount of reducer will make the ink more workable.
Thin Some Colors More Than Others
Since our test job is a three-color print we will thin our lightest colors a little more. This will generally be the FIRST COLOR YOU PRINT and it needs to penetrate INTO the garment more than the others so you won’t pick it up on the bottoms of the other screens. If black is our last color, we can thin it less. It needs to lay on top of the other colors and will blend in with the undercolors if it is too thin.
Stir the Ink First
Plastisol ink tends to get a little thicker or “body up” when it isn’t in use so you should ALWAYS STIR THE INK BEFORE YOU THIN IT. By stirring the ink you will find out if it really needs thinner. I prefer an ink that is smooth and creamy to one that is so thick that you break the stick trying to stir it.