Squeegee model selection from the manufacturer Pfleiger Kunststoff
For peeps screen printing frequently, it’s common knowledge that adequate screen tension, proper mesh count, suitable ink viscosity, minimal off contact, appropriate pressure help for good printing results. But how much do you appreciate your squeegee’s contribution to a successful result? Cousin squeegee is very much undervalued most of the time. This little guy is the player in the play-offs to get your print rolling the right way. Sometimes trouble shooting could be as easy as understanding how to pick the right squeegee for your game and how to keep cousin squeegee happy through proper maintenance.
What is a squeegee made of?
I usually refer to the word rubber when I talk about squeegees, but that is not the whole picture. There are a couple of different synthetic materials involved. Roughly, you can differ between three basic types: rubber, neoprene, and polyurethane. The least expensive is natural rubber. But as all natural materials, this is more sensitive to solvents and abrasion. The trade off is that it’s cheaper, but it has a shorter shelf life. Neoprene, a synthetic rubber compound made from a chroline derivative of acetylene, is pretty popular and more cost effective. It offers better resistance against chemical abrasion. Polyurethane, a synthetic plastic material, has the longest shelf-life and is intended for extended use on automatic and semi-automatic equipment. It is more costly due to higher endurance.
Stress test in durometer: Run squeegee run!
Before we get into endurance, be sure you know the length of your squeegee’s marathon. Your squeegee needs to be at least 1–2 inches larger on both sides than the image to be printed. Not having sufficient overage on the sides, can result in distortion of the image, or registration problems in the following colors.
But back to durometer. When I go, for example, to Chicago Silkscreen Supplies to get replacement squeegee blades, I am asked for the durometer range I am looking for. This number indicates the materials ability to resist bending. It is measured by a durometer gauge, and is based on standards established by American Standard Testing Materials procedures. The higher the number, the harder the material. It’s unit is Shore A scale, with the index of 1-100. The instrument used to measure this is called a durometer. But there’s also other criteria, like the color coding of the squeegee materials from manufacturers. This can, of course, vary, but from my experience and observation these color codes have been pretty standard across the board.
Choosing a squeegee durometer depends also on your substrate, mesh count, and screen tension. For example: 55 durometer is very soft, soft enough to conform to varying garment thicknesses or uneven platen surfaces. However, this range can bend under high squeegee pressure. 80 durometer is a range for harder squeegees. This range is far less forgiving and will not print an even layer of ink on an uneven surface, such as a textured weave. It can stand up to the high pressure needed to print at high speed or with high-opacity, high-viscosity thick plastisol inks.
The high tech age has gone blade runner with this technology (see the pictured models above from the Pleiger Kunstoffe). Industrial screen printing takes advantage of the multi- and triple-core durometer blades that have mixed combinations of rigidness. These are like sandwiched rubber layers.
What’s your squeegee’s profile?
The profile of the squeegee does matter. It determines the thickness of the ink deposit laid down and the effectiveness of the squeegee with different substrates. For example, for puff or glitter ink, or a white primer, mesh counts coarser than 96 threads/in. you might need to use of a bullnose profile. The common profile in graphics printing is the square blade and is usually 9 mm thick and 50 mm tall. These are common, and mainly used on cylinder, textile, or manual presses. Rounded Squeegees are generally limited to the textile industry, and are used when a very heavy deposit is required. Beveled blades are used for printing rounded surfaces where fine definition is required. The single beveled blades are great when printing heavy solids. While double sided beveled blades are more efficient on high-speed automatic machines. I highly recommend downloading this spec sheet from pleiger-kunststoff target=”blank” where the different profiles of the squeegees is declared in depth. It also offers specifics for angles the squeegee needs to be held at or mounted to function best. It’s a great learning chart to get a feel for the vast range of squeegee profiles that industrial screen printing has developped.
Don’t let your squeegee be a free agent!
Squeegees need care, from storage to the knowledge on how to use them most effectively. If you buy squeegee rubber in a role, unroll it immediately! Always store the blade hanging or store it horizontally. The materials of a squeegee will react to temperature changes and solvents. So don’t store them next to a heater, be aware what squeegee you use for what kind of printing. Most of all, though, be aware that these materials change over time. For example, as the print run evolves the squeegee will get softer. This can explain why your ink is being layed down thicker towards the end of a longer print run. By rotating your squeegees you can prolong the squeegee’s life by up to 40%. At $1 per inch, you might just save up for a first-time trip to Bermuda?
References:
Pfleiger Kunstoff, Printersedge, Siebdruck und Serigraphie by Andreas Rombold, E.A. Seeman Verlag