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Screen printing: 5 applications per number of threads
A screen printing (or screen-printing frame) is a frame with a very tightly stretched and glued mesh (there are other ways too - see end of article). It is through this mesh that the ink, using a squeegee in the printing process, it passes evenly through the screen and consequently prints the desired substrate.
⧗ reading time - 9 to 11 minutes ⧗
the screen printing frame
Frames can be made of wood, aluminum or iron, the first two being the most common.
Iron frame
Although the iron is quite stable for fixing the mesh, it is very heavy and makes it difficult to handle, increasing the physical wear and tear on those who use it. What's more, it probably doesn't have an anti-corrosion treatment and constant washing can cause the iron to rust.
Aluminum frame >
Aluminum screen printing mesh, due to its light weight, structure and stability, as well as water resistance, is generally the best option. They are light to transport and handle, do not rust and are very stable, ideal for stretched mesh.
aluminum frame
Wooden Board >
Wood is cheaper than other elements and its construction may be more affordable compared to welding steel and aluminum, which makes its use quite common in screen printing. On the other hand, it is less stable due to its constant interaction with its surroundings.
The absorption and loss of water can be responsible for slight deformations and it is therefore advisable never to submerge it in water. The screen can be washed, just enough to remove the ink, emulsion and/or dirt, and it is not advisable to dry them directly in the sun. Although they may swell or deform, they can last for many years and are a valid option for many jobs.
wooden frame
What is screen printing?
Mesh size and number of threads
The fabric currently used in silkscreens is polyester. But as the name silkscreen (also known as screen printing) indicates, silk was once widely used for this purpose. However, synthetic fibers such as polyester or nylon have replaced silk due to their strength and resistance. Polyester is currently the most widely used synthetic fiber for screen printing.
The mesh is made up of very fine threads, between which the paint will pass. It may be imperceptible at first glance, but the mesh can be more or less closed. For this reason, the screen is always identified with a number and a letter. It's common to see the identification, for example, 72T on the screen. This means that the mesh has 72 threads per square centimeter.
The common numbering, subject to small variations, should be very close to the following: 43, 55, 72, 90 and 120. But pay attention to the numbering, as you can also find measurements in inches/inch. For example, the brand SpeedballAmerican knits are numbered differently - see the conversion table below. A 43 mesh is very open, with fewer wires per square centimeter, while 120 is a very closed mesh.
Metric conversion table for screen printing meshes
yarn/cm
wires/inch
43
109
55
140
72
183
90
229
120
305
For the conversion we used the reference of 1 inch = 2.54 cm.
To convert, simply divide the number in inches by 2.54. Example: 140/2.54=55.
In centimeters, you'll generally find a number of standard threads between 43-140T. So if there's no reference to the units of measurement and the value is very high (200/300), you know from the outset that the unit is inches.
If we transfer this diagram to a pixelated grid, we can see that a 120 mesh has greater definition and should be used for printing very fine details or substrates with little or no absorption. The lower the number of wires, the lower the definition.
The fact that it is less or more open (as well as the thickness of the wire) influences the amount of paint that passes through the mesh. In this sense, the fewer the number of wires, the more open the mesh, which means that more paint passes through to the substrate. In the opposite direction, the greater the number of wires, the more closed the mesh, and therefore the less ink passes through to the substrate.
White and yellow mesh
Why are there white meshes and yellow meshes in screen printing? The white mesh, in the engraving process, reflects the incident light and can scatter the light between the mesh and the photolitho. Yellow mesh absorbs light without reflecting it. Depending on the engraving conditions (e.g. no vacuum), the yellow mesh may be better, the higher the image definition. That's why it's common to find meshes with a higher number of threads (≥ 90T) with a yellow color.
What number of wires is recommended?
In practical terms, if you have a design with a lot of fine details, ideally choose a more closed screen, which will guarantee you a better result. This is because, due to its denser structure, we'll get a more defined result.
However, the type of substrate we are going to print on can change our choice. Substrates can have different characteristics, in their texture or level of absorption. Fabric absorbs more ink than paper, metal or glass. In this sense, when we print on fabric, due to its absorption capacity and in order to obtain a uniform print, it can be beneficial to choose a more open screen. This is because more ink will pass through the mesh. But each fabric has its own characteristics, because a cotton fabric is not the same as a silk fabric, which will absorb less ink.
Even the type of ink we use can influence the choice of mesh. For example, there are inks made up of larger particles (such as metallic effect inks), which require a more open screen.
With the experience gained over the years, these choices become easier, but the less we know about the substrate, the greater the need to carry out tests in order to find the best solution.
By analyzing the numbers listed above - 43, 55, 72, 90 and 120 - we can already conclude that 43 is a more open mesh and 120 a more closed mesh. A mesh size of 72 is considered a medium mesh, suitable for either paper or fabric (to mention the two most commonly used substrates).
In theoretical terms, and according to the above analysis, we can separate meshes 72/90/120 for printing on paper and meshes 43/55/72 for printing on fabric. We can choose between them depending on the level of fine detail of the image we want to print, as well as the specific characteristics of the substrate (absorption capacity, texture, etc.).
However, practice must be valued, and everyone's experience may change some options. Printing fabric with a 90 mesh may be ideal for some, but the wrong choice for others. The important thing is that, with accumulated experience, you can make these choices naturally, according to the substrate and image to be printed. If you're just starting out or are a beginner, you can start by following these tips on the number of threads in the screen printing mesh:
Types of application by number of wires
43T - Printing on fabric with opaque or special colors, on dark backgrounds. More open mesh, greater ink flow.
55T - Suitable for printing in general, on dark and light fabrics, with medium details.
72T - Printing (light and medium colored fabrics) and printing in general, with some fine detail. We consider this size to be a medium mesh, so if you want a silk screen for printing on paper, but also on fabric, we recommend this number of threads.
90T - Fine detail and bitmap/halftone printing on paper and surfaces with little absorption. Also suitable for fine details on fabric (printing can be challenging for beginners).
120T - Printing very fine details and bitmap/halftone on paper, glass, ceramics, plastic, metal and other materials with little (or no) absorption capacity.
Important: Degreasing
Before emulsifying a screen printing screen, it is advisable to wash and degrease it. Whether new or used, the degreaser will remove any dirt or grease.
Grease, or dust, can separate the emulsion from the mesh, causing a common problem that results in small spots without emulsion. If grease contamination is all over the mesh area, the emulsion can break easily
In our experience, it is also particularly important to degrease new fabrics. Although they have never been used, they may have been contaminated by handling or even by the mesh manufacturing process.
Always use a brush dedicated to the degreaser, different from the brush used to remove the emulsion.
Our
screen printing
All our screen printing canvases are made from high quality polyester fabric, tensioned appropriately, respecting the properties of the fabric. The fabric is glued to the frame using a two-component waterproof glue to ensure maximum hold.
The screen printing frame is made of aluminum and we have two sizes available, A4+ and A3+ (sometimes you'll also find A2+ screens in stock).
In terms of the number of threads, you can find the following knits: 43T, 55T, 72T, 90T and 120T.
If you're just starting out and aren't sure what number of threads would suit your project best, choose a 55T screen for all textile printing and 72T or 90T if you're interested in graphic work. If you want a screen for printing on paper and fabric, you can choose a 72T screen. For more specific projects, you may need a screen with a different number of threads.
But as this article points out, there are several aspects to take into account. While a more open screen is beneficial for printing on fabric, a more closed screen is better for images with finer details. You'll have to strike a balance between these two aspects and with experience you'll know what suits your printing method best.
Glue, staple or pin?
In the introduction to the article, we mentioned that there are other ways of attaching the mesh to the frame on a screen printing screen, apart from using glue.
In wooden frames in particular, you'll find other fixing systems, such as staples and mortise and tenon. In the case of the mortise-and-tenon system, the wooden frame consists of two frames that fit together, allowing the mesh to be wedged between the two.
With staples, you need a frame, like the ones used to glue mesh, and staple along the entire frame.
Both of these do not guarantee that the mesh will have the necessary tension. Even with staples, when the mesh is well stretched, you can get a reasonable tension. Staples do not allow the mesh to be fixed completely evenly, as is the case with glue.
We are not rigid in our adherence to a particular principle, but we have emulsified enough badly tensioned screens to know that it can go wrong. So our advice, apart from a few exceptions, is always to opt for a screen-printed canvas with the mesh glued* to the frame.
*It must not be an ordinary product. The glue used is suitable for this purpose. It is bi-component and can work on aluminum, iron and wood frames.
Conclusion
The screen printing screen, a crucial element in the printing process, is characterized by a mesh that is stretched and glued to a frame, providing an even distribution of the ink over the substrate. The preference for aluminum in terms of the frame comes from its light weight, stability and resistance to water.
As for the fabric and its density, which is predominantly polyester these days, it is represented by a system of standard numbers such as 43, 55, 72, 90 and 120T (there may be others).
The mesh plays a crucial role in defining the image and the amount of ink that is transferred to the substrate, whatever it may be.
The more open meshes, associated with a lower number of threads, are suitable for woven fabrics, while the more closed meshes, with a higher density of threads, are a better choice for reproducing fine details, especially on substrates with a lower absorption capacity.
The choice of mesh color, whether white or yellow, and the number of wires are determining factors in the effectiveness of the process, and are adapted to the characteristics of the substrate and the complexity of the image to be printed. Although testing is essential in order to master and find effective approaches.
We recommend that you have several numbers of threads, so that you can choose the right one for each type of project. However, to begin with, a 72T screen printing medium may be the most suitable when you want to print on paper and fabric, for example.
Screen printing is a complex combination of choices and experience plays a crucial role in decision-making. As with any other craft and technique, experience and experimentation are the solution to mastering and discovering what works best for each individual.
Screens with engraving
At FICA Oficina Criativa, in addition to selling screen printing, we also offer an exhibition/engraving service. Screen prices vary according to size and number of threads
Screen printing material
In addition to screen-printing services, you can find various materials and consumables in the store: screens, squeegees, scrapers, emulsion, hinges, adhesive spray, water-based inks.