Screen Printing: Types, Development of Screen and the Printing Procedure

Screen printing is a way of printing images by forcing printing ink or paste with the aid of a squeegee through a specially prepared screen block to register a print on a substrate such as fabric, paper, leather, T-shirt etc. It is also referred to as Serigraphy or Mitography. This printing technique is widely used by several artists and most printing houses for the execution of their projects because it can be used in printing on virtually all surfaces such as papers, plastics, cloths, leather, glass, wood, rubber etc.

There are two main types of screens that are used for screen printing. Temporal Screens last for a shorter period of time. They are suitable for registering single or limited prints on clothes and papers. They are very easy to prepare and does not require a lot of money or effort. Examples of temporal screens are paper stencil screens and candle wax screens.

However, permanent Screens have a very long time span and if properly cared for, can last forever. They can be used in printing multiples, hundreds and even thousands of prints. Their preparation in comparison with the temporal screens demands considerable effort and money. Examples of permanent screens include photographic screens, lacquer screens and shellac screens.

There are various ways of developing screens for printing. Some of these have been detailed in discussion below.

1. Paper Stencil Screen Preparation- This paper stencil screen is very similar to the stencil preparation though this is an extension of it. It involves the transfer of the finished design onto the paper to be used, while cutting out the positive areas (the image to be printed) of the paper. The prepared stencil is then attached to the stretched screen block with the aid of a masking tape. Enough allowances are left to serve as ink reservoirs. The screen is ready for printing.

2. Candle Wax screen/Shellac Screen /Lacquer screen preparation- The preparatory processes in these methods of screen preparation are the same. The only difference is the material used in coating the negative areas of the screen which may either be molten wax, shellac or lacquer. The finished design is transferred onto the stretched screen block. With the aid of a brush, apply the molten wax or thinned shellac or lacquer to block the negative areas of the design. Test screen for pinholes by doing a test print. Block pinholes if there are any. The prepared screen is ready for printing. Lacquered screens are very durable and more economical in terms of quality and quantity. They are very good for simple, bold designs.

3. Photographic Screen Preparation- The photographic screen preparation involves the use of light in developing or bringing out designs onto the screen. The sources of the light can be natural or artificial. Therefore, there are two main ways of making photographic screens thus the use of the solar energy (sun) during the day and the use of the strong fluorescent bulbs in the exposing or shooting box. In all these two ways, the screens have to be coated in the darkroom with a solution of photo emulsion mixed with a sensitizer. The screen is placed in the dark room to dry.

In the solar energy method, the inside or hollow part of the coated screen is filled with a sack of fine sand on a flat wooden board and turned upside down. The positive part of the paper (where the designs are) is placed on the frontal part of the screen and covered with a piece of cloth. The whole thing is exposed to the solar energy (sun) for some few minutes. The duration is dependent on the intensity of the sun. The screen is then removed and washed under running water. The design areas will be left open with the negative areas blocked.

In using the developing or shooting box in the dark room, after the screen is coated with the photo emulsion and sensitizer solution, it is left to dry. The design is then placed with face up on the glass of the shooting box. The frontal part of the dried coated screen is placed on the design with the inside or hollow part up. A sack filled with fine sand or heavy clothes hinged with stones are placed in the hollow part of the screen just to ensure firm contact between the glass plate, the paper with the design and the screen. The lights in the shooting box are switched on for about five minutes. The duration can be more or less depending on the number and watts of the fluorescent bulbs in the shooting box. The screen is removed and washed under running water. Afterwards, it is dried and ready for printing.

The following steps are followed when printing with prepared screens.

1. Prepare the printing table.
2. Place Substrate (t-shirt, hanky etc.) on the printing table.
3. Position the screen (hollow side up) on the substrate.
4. Fetch little printing paste into the non-image area (ink reservoir).
5. Draw pull paste across the image area of the screen with the squeegee tilted at a reasonable angle to register a print.
6. Go over the print if deeper print is required.
7. Gently remove, wash and dry screen for future use.
8. Allow print to dry and iron design to fix.

There are some important tips that should be noted when printing. These are:

-Correct placement of screens- The artist should pay close attention to how he/she positions the screen on the substrate or material to be printed. If screens are wrongly placed on the substrate it would result in wrong registration of designs at designated areas of the substrate. Also, if the prints are repeated on the cloth in a special pattern or arrangement, there will be gaps or disorderliness in the arrangement.

-Appropriate pressure on the squeegee- The pressure exerted on the squeegee should be moderate and well thought of. This is because if the pressure exerted is less, some areas of the screen will not be registered in print. On the other hand, if a lot of pressure is exerted on the screen, it will result in the blurring of designs on the substrate. This means that the printing ink or paste will extend beyond the boundaries or edges of the design. Therefore, the pressure exerted on the squeegee should not be too light neither should it be too much.

-Instant washing of screens- The screens used for printing should be washed immediately after printing to avoid the blockage of screens. This is due to the fact that when the printing ink residue is allowed to stay on the screen for sometime it ceases to be washed off from the screen resulting in its blockage. It is appropriate then to wash the screen right after the printing with soapy or warm water and foam to remove all ink residues. However, it should be washed gently otherwise it will result in the creation of pinholes which are small areas of the coated screen which are free from the coating solution or the tearing or reduction of tension in the taut stretched screen.

Developing printing screens manually or mechanically is the choice of the artist based on the resources at his disposal and the time s/he has to deliver. Each of the screen development processes and its printing procedure requires great patience and determination so as to produce accurate duplication of designs.

Screen Printing Tips: Helpful Info on Silk Screening White Ink and Screen Print Technique

It seems that one of the most common problems new screen printers run into is printing white ink. I’ve heard a lot of questions like: Why do all my other colors print fine and white is so tough? Why is it that my white ink is so thick? Why can’t I get a smooth white ink? It’s always rough and seems to have texture to it. Is there anything I can do to thin my white ink to make it easier to print? Also comments like: “Our white ink is bad, it comes off after only a couple of washes.” “There’s something wrong with my press, it prints fine when I am printing on white shirts, but when I print on dark shirts the white ink is very blurry.”

Unfortunately, the answers to these quarries usually lie in the printer themselves. No, your white ink isn’t defecting, your press probably works fine, and you shouldn’t need to thin the ink. Yes, you probably need to change some variables and techniques during the printing process. The truth of the mater is, the answer is in the question all along.

So why does the screen printing process work fine for a while and then as soon as you start printing white ink, smash, a road block. The truth is, you may have been doing the wrong things the whole time, it just didn’t show up yet . It’s like swimming, sure you can dog paddle and flounder around the pool all day. However, when it comes to swimming a long distance, without the proper techniques you’ll work twice as hard and get half as far.

Printing on light garments is much easier than printing white on dark garments. On a light garment, not as much ink is required to achieve good coverage. Also many times you’re working with thinner inks. Ink varies in viscosity according to how much pigment it has in it. For instance, a black ink is almost always going to be printed on lighter colors, the pigments needed for the black to show up are considerably less then the pigments needed for a white ink to cover a dark garment. Thus, you’re black ink is much thinner and easier to work with. You can do almost every technique wrong when printing black ink on a white shirt, and there’s still a good chance that your final print will look pretty good. Since the ink is thinner, it passes through the screen mesh much easier, with less force, and clears the screen better. (For those unfamiliar with the term “clearing the screen,” this defines the point when all ink is cleared out of the screen mesh and properly transferred to the shirt.)

So basically when setting up a screen printing job that requires black ink on a white shirt, you can use the wrong screen mesh, have no off contact, and print with the completely wrong squeegee technique and still get an “OK” looking final print. However, if these same wrong techniques are tried when printing white ink, uh oh, game over! The unfortunate thing is, many printers start out this way and teach themselves completely wrong. In fact, this is how I learned. It’s not the end of the world though!

The first thing you’ll have to understand and come to terms with is the fact that white ink is probably going to be the thickest ink you’ll ever use. To achieve a bright white image on a black shirt, the ink has to be opaque which in turn means thicker. Sure you can find thinner white inks, or try to reduce the thicker ones, however you’re defeating the purpose and you’ll end up printing twice as much to try and achieve the same result. On the other hand, if you learn how to print correctly, then printing white is like taking a walk in the park.

Over the past several years, every ink manufacturer in the country has been on the hunt for the “best” white ink on the market. Yes, they’ve come a long way. In fact twenty or thirty years ago white on black looked more like a light tan or gray than white. Now with inks available like Triangle Phoenix White or International Coatings White, you can achieve maximum coverage with minimal passes. Still, white ink has to be loaded with pigment which means it will always have a high viscosity.

So what’s the trick? How can you print white ink like the
pros.? The answer usually lies in a few simple changes to your setup and
technique. Apply these changes and really, it’s not that hard.

Before we delve into techniques, let’s first discuss a little bit about pre press and setup.

To properly setup a job using white ink you first must
understand a little bit on how to select the proper mesh size. Because white is
thicker, you want to print through the lowest proper mesh size that applies to
that print. If you try and print white through a higher mesh screen which has
much smaller holes in it its going to make it much harder to push the ink through the screen. It’s also not going to allow as much ink through the screen as a lower mesh would.

Typically you want to print white through mesh sizes ranging from 110-156. Granted sometimes the image dictates a high mesh count. For instance, since a half tone or fine line drawing cannot hold on a lower mesh screen, you’ll have to use a high mesh frame and apply more passes to achieve a bright white. For the most part however, you’ll want to use the lower meshes so that a larger amount of ink is deposited on the shirt.

The second part of setup is to insure the screen is adjusted properly on the press. You want to be sure that you have a proper off contact of about 1/8-1/16 of an inch. Since white is a little thicker, you may want to go with a slightly higher off contact then normal, perhaps around 1/8 of an inch. Off contact is the height between the screen mesh and the substrate you are printing on.

Proper off contact also allows the ink to be cleared from the screen mesh easily by releasing the mesh upward directly after the print stroke leaving all the ink smoothly on the shirt. One thing that you also want to be sure to apply when printing white ink is an off contact tab. This is a small piece of material (ie. a penny, cardboard, paper, a piece of plastic) that is the height of your off contact. This tab is placed on the end of the screen frame where it hits the top of the neck platen and not the shirt. By using an off contact tab, you insure that your off contact will remain through the entire print stroke.

The tab keeps the end of the screen up although you are pushing down on the mesh during the stroke. Without an off contact tab, you may find that you have a harder time clearing the mesh because the screen wants to stay flat against the shirt with ink stuck in it.

If you don’t have the proper off contact a few problems could arise. If your off contact is too low then you will not be able to clear the screen properly. You should see the screen mesh bounce off the shirt and be able to see the ink and the shirt through a cleared screen mesh. If your ink stays in the screen mesh and the screen mesh sticks to the shirt, when you pull the screen up your ink will look very rough and parts may pull back off the shirt. If you’re having this problem you may need to raise the off contact a little bit. Also, this problem could arise from your actual print stroke which will be discussed later.

On the other end of the spectrum, if you’re off contact is too high; you’ll have to push down extremely hard on the squeegee in order to get all the ink down onto the shirt. I’ve been out to shops to help customers who literally had almost a half of inch of off contact. If your off contact is too high, not only will it be hard to transfer the ink onto the shirt, but there’s a good chance that your screen won’t come down in the same spot every time. This could cause a blurry image or double images after a flashing. A proper off contact is extremely important for a good looking image and an easy print.

Next let’s take a look at technique. The majority of the technique in the screen printing process involves the print stroke. This includes squeegee angle, pressure, speed and release. That standard tendency of a new printer is to literally smash the ink through the screen by pulling the squeegee across the screen with an extremely low angle.

When using thin inks, this impropertechnique could work because the ink passes through the screen so easily. However, if tried with white, you’ll not only have trouble passing the ink through the screen but also have very blurry images because you’re pulling the screen mesh so hard. Your squeegee should actually be about an 80-85 degree angle facing toward you. You should also focus your pressure over and down on the print and not on pulling the squeegee against the mesh.

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Many new printers stand back from the press, you actually need to stand over the press to focus your pressure down and not back. When your pressure is focused down, then you simply move the squeegee back over the print. With the proper squeegee angle, all of the ink will properly shear through the image and over your screen. In fact you should be able to run your finger over the design after its printed and barely any ink should show up on your finger.

Now let’s talk about the speed of your print. When we instruct printers to use the proper squeegee angle and pressure, the first impulse they have is to move the squeegee about the speed of a turtle. If your speed is too slow you won’t be able to properly release and clear the screen. After a print stoke, many beginners tend to sit back and look at their print, then slowly pull up on the squeegee not allowing the screen mesh to bounce back up leaving ink still stuck in the screen. After a faster stroke, you need to almost give the screen a little pop in order to get the mesh to bounce back up leave a smooth crisp print on your shirt. This is achieved by a simple flick of the wrist, the same flick you would make to insure that you pick up all the ink on your squeegee blade. Only to create this pop and release the screen, the flick must be done a little faster.

Finally, when flashing in between passes, you must wait until the shirt cools down a little until you print again. This is much easier to achieve on a multiple station press because it allows the pallets to cool down. On a single station press you may have to wait a few moments and wave your hand across the pallet to cool it down.

If the ink is too hot from theprevious flash, you may have trouble clearing the screen because the ink will want to stick instead of release the mesh. It could also cause ink to partially cure in the mesh. Since white ink is thicker and you apply more layers of it, you MUST insure a proper final cure.

White ink tends to reflect heat away instead of absorbing it in. This means that the ink and the entire print area must be cured from top to bottom at 320 degrees for about 45 seconds. Obviously the best way to cure white is in a conveyor belt dryer, however if you are using a flash dryer you want to be sure that the whole design gets the same amount of heat.

One of the best ways to insure a proper cure is called the stretch test. Since your white image will be a little thicker, this test is easy to read the results. After your shirt is cured, simply take a small section of your design and stretch it slightly between your fingers. If the design sticks together like plastic and stretches well, then it is cured and you can continue with those curing parameters. However, if the ink cracks or breaks apart, this means the base of the ink is not cured properly and you need to increase yourcuring time for the shirt.

By following these steps and techniques you should find printing white ink a little easier. Granted, because there are so many variables involved in screen printing, you may have to work a little at it and modify slightly. However, after a few times printing the right way, you’ll start seeing better results and have fewer problems.

Understanding the Basic Screen Printed Bags Terms

Screen printed bags and products are the first choice of many people now. Not only it is cost effective but also opens wider doors of different styles and designs of exactly your choice. Screen printed products look like finely painted items and due to this its demand is on rise and the screen printing business is booming. But before getting in screen printed bags business, you should know some basic terms used in this industry.

1. The term “Artwork”:

It refers to the picture, caption, slogan or statement you want to print on your t-shirt. This is the first step in screen printing and for this purpose many softwares are available in the market. The important thing here is to do it in vector format. For printing the artwork generally Corel Draw and Adobe Illustrator are used.

2. The ‘SEPS’:

The ‘SEPS’ or in common words the separations are the separate films on which each color is printed. This will aid in burning the images of each different color on the screen to give a clear fine print.

3. The Screen:

It is a square tool which is made of aluminum or wood. On it a tightly woven net or a “mesh” is firmly stretched. It is used for effectively burning the print on the t-shirt.

4. The MESH:

As mentioned in the third point, it is a web like meshy material which is tightly stretched on the screen. It is porous in nature and has small pores of various sizes which allow the ink to seep through it in different quantities depending upon the print design. The screens have varying mesh count depending upon the design and lesser mesh count screens allow more quantity of ink to pass through it.

5. Emulsion and its use:

This is a liquid which is used to block those pores of the screen where you don’t want the ink to pass through. Emulsion is applied on the screen and when it dries up in the dark room, blocks way the pores. In this way an accurate impression of the print is framed on the screen and nothing other than the desired print appears on the shirt.

6. Coat:

It refers to blocking away unnecessary pores on the screen by coating it with the emulsion.

7. The burning process:

Here halogen light or very high wattage light bulb is used to burn the design on the item to be printed. The image blocks out the light on the screen and here the emulsion remains soft and gets eventually washed out and the ink seeps through it to create the impression. In this way a fine print is produced.

8. The use of Halogen and high wattage bulb etc:

These permanently block off the pores on the screen and are used for creating a sharp impression of the print on the screen. In this way a clear print in burned on the silk screen to get good end results.

9. SQUEEGEE and its purpose:

This is used for finely smearing the ink all over the screen.

10. PLASTISOL:

This is the special ink used for screen printing purposes. It has distinctive properties suited to its purpose e.g., it does not dry off even when left out until it is specifically dried off at high temperature.

11. The Flash unit:

It dries up the ink sufficiently to get another color printed on it. While toping a color with another print, flash unit is used to dry the initial color up to a certain limit then the next color is applied.

12. The use of Pallet in screen printing:

It is a piece of wood on the top of which the shirt to be printed is placed.

13. Auto press:

This is a huge printing unit in the form a of an equipment which can print up to 14 colors. It is used for collectively printing off the shirts.

14. The conveyor dryer:

It is used to dry up the shirts at the final stage of printing.

For more information about this industry, please don’t hesitate to Contact Us!

The Screen Printing Screen: Know Which One To Choose For Your Next Design

Screen printing is an art form that just about anyone can enjoy. The materials are affordable and easy to find; simply walk into a crafts store or go online to find a starter kit that contains all of the supplies and instructions you need to start printing. And the process is uncomplicated and straightforward; follow a few steps, allow time for the ink to cure, and your print is complete. But before you unassumingly purchase an indiscriminate starter kit, keep in mind that there is one component to printing that can make your design a picture perfect masterpiece or a disappointing muddled mess.

The screen printing screen, or mesh, is arguable the most important item in the screen printing process. Choosing the proper screen will make all the difference – whether you are rendering fine details, layering background colors, or printing on different types of materials, all printing projects require ink passing through the screen in order to create the print. It is crucial to select the appropriate gauge and fabrication for your design, otherwise, your design could be compromised.

Screen printing screens come in an array of fabrications. The most common screen types are manufactured from either plastic or metal. Plastic screens, made from nylon, vinyl, low elongation polyester, or monofiliament polyester, are generally inexpensive, and are found at many craft stores and online. Because of their flexible nature, plastic screens can be readjusted and tightened within the printing frame. Plastic is also a sturdy, resilient material that can stand up to repeated use.

On the other hand, metal printing screens are quickly becoming a formidable choice in the industry. Many metal meshes are manufactured from stainless steel, which is incredibly durable over time, making it a more economical option. In addition, stainless steel screens hold their shape longer than plastic, since it is a stronger material from the onset. It, too, can handle the stresses of printing, but will also rinse more cleanly and not absorb ink over time. With plastic, once the fibers begin to wear down, they will soak up more ink with each print.

Whichever fabrication you select, both plastic and metal screens come in a wide variety of gauges. This size of the screen openings, or apertures, will depend on the width of the weave. In other words, the wider the weave, the larger the aperture. This is important because smaller gauged screens will let less ink pass through its openings. As a rule, for larger shapes or backgrounds, a larger gauge is preferred since there are less details being printed. For smaller shapes, delicate detail work, or lettering, a finer gauge is recommended.

Because the manufacturing process has perfected the production of plastic and stainless steel screens, it is easier than ever to create professional-looking prints. While most starter kits will include a screen, it is worth researching the different kinds of screens for the designs you wish to create. High quality screens no longer have to come attached with a premium price.