Detail And Halftones Using Higher Mesh Counts
As beginning screen printers, many people start with one or two screens with the same mesh count. Some people buy used equipment with a few screens and may have more than 1 mesh count on hand. Yet other people printing at home may not even be using screen printing mesh. But it is important to understand what the mesh count means and how you can use mesh counts to make printing your designs easier.
We will try not to get technical here at all. But there are certain principles you must understand in order to choose your mesh appropriately for the job you are printing.
Mesh geometry is the description of all two and three dimensional aspects of the mesh construction. The two basic factors in mesh geometry are the mesh count and the thread diameter. The mesh count refers to the number of threads per inch contained in the mesh. The thread diameter refers to the diameter of the thread before it has been woven into the mesh.
It is important to remember that mesh geometry will define the characteristics of the mesh. The mesh opening, mesh thickness and the theoretical ink volume obtainable by the mesh are all determined by mesh geometry.
Mesh geometry affects:
- Printability of fine detail, lines and halftones.
- Crisp resolution of edges in the design.
- Ink release properties.
- Printing speed in relation to your ink viscosity.
- Ink volume thickness.
- Ink consumption during printing.
Please note that this article is geared more for manual screen printing as opposed to automatic screen printing. The same printing application will call for different mesh counts when the job is printed manual or automatic. More specifically mesh opening rather than the mesh count can be the determining factor in automatic screen printing.
Generally, a lower mesh count like 110 will be easier to print with and deposit more ink. But when you want to print fine lines and detail, the 110 mesh becomes difficult to work with. 110 mesh is not the default mesh for textile screen printing. You need to choose the mesh appropriately for your printing application. The emulsion is not able to stay adhered to 110 mesh in finely detailed areas and often produces jagged edges in the final print. And 110 mesh is most always white. White mesh causes the light to bounce off and scatter in the exposure unit when burning your artwork. This can affect your ability to render detail as well. This will always occur with white mesh of any thread count. Having a point source exposure unit is better for fine detail and halftones as well.
An easy way to obtain the detail you want is to move to a higher mesh count like 195 or 230. Once you get to 200 mesh counts and above, they are most often dyed yellow or amber/orange. The mesh is dyed in order to eliminate or reduce the light scattering effect of white mesh. To render fine detail or halftones a dyed mesh is preferred so that stray light is actually absorbed into the dye, rather than bouncing around.
Working with higher mesh counts that are dyed is a little different in a few aspects. It is less forgiving all around.
Some important notes to remember with higher mesh counts and dyed mesh:
- The dyed mesh will increase your exposure time.
- Pinholes and premature stencil wear or breakdown can be a problem if the screen is
not well prepped for coating with emulsion.
- The thinner stencil, necessary for fine detail, wears quicker over longer print runs.
- Higher mesh counts hold less emulsion creating thinner stencils. Strong adhesives like tape
can pull the emulsion off of the mesh thus ruining your stencil. Proper mesh prep can eliminate
this as well.
- Halftones need to be created specifically for the mesh count being used to avoid moiré
patterns.
- Higher mesh counts generally cost more.
- Higher mesh counts are harder to stretch without tearing or popping.
If you choose your mesh appropriately for the artwork you are printing, then you will have an easier time achieving your end goal. Don’t forget to read the article “Mesh Count And Thread Diameter Nomenclature” under the More… tab in the Printing Articles section. It will help you understand and make use of mesh terminology.
Printing A White Under Base
This article is intended to introduce you to white under base printing. This can be a very technical process and requires that you are familiar with the technique. White under base screens are often burned on 110 mesh. If you are printing fine detail or halftones on top of the white under base, you will need to use a higher mesh count for the under base in order to provide a smoother more consistent surface. Printing halftones or fine detail on a rough under base will produce poor print quality. Subsequent colors may require a higher mesh count depending on the inks you are using and your artwork. High quality, high opacity inks are necessary for obtaining great results easily.
When printing vibrant colors on black or dark garments it is often necessary to print a white under base first. This is due to the fact that many plastisol textile inks do not have the opacity to cover well on dark garments. A white under base is nothing more than a white spot color print in the shape of the artwork for which the color is intended. It is printed first to provide a base for the colored ink to rest on. The under base is flash cured before the remaining colors are printed.
The under base will actually fill the knit some and keep the colored ink to be printed on top from soaking into the fabric of the shirt and thus losing its intensity as well as its coverage ability. It is somewhat like a primer when painting a house. The primer seals the surface and presents a good surface to paint onto.
In most cases, when printing dark garments, you will want to print a white under base. Some plastisol inks are made to be “high opacity”. These “HO” inks are intended to be printed on a dark garment without the need for a white under base. Many of these inks are great and work very well. Sometimes it will be necessary to do a hit-flash-hit in order to achieve the coverage you desire. But most will work well using 110 mesh stretched tight. And as always, you would want to avoid the hit-flash-hit to keep production time at a minimum. Wilflex makes great high opacity inks for dark garments. Most of their inks will cover well just using 110 mesh.
Heat buildup is a problem that has to be resolved with cool down stations. If you are printing with a fixed pallet and print head, you will need to let the pallet cool between prints. This is very important. And be sure that your flash dryer is not heating the screen above it. With a fixed pallet and print head you will need to set the flash dryer so that it flashes the under base quickly thus limiting heat buildup time for the screen and pallet. It is best to use a rotary press for this or any multi color printing with a flash cure.
Creating your artwork for multi color jobs on a white under base can be difficult. I highly recommend letting someone do this for you if you have never done it before. You will be able to learn from the film and setting up on the press all the “how’s and why’s”. If you are just printing 1 color on the under base, then you should be able to set it up yourself.
The artwork for a 1 color print with an under base should be choked some. That is to say that the color over printing the white under base should over print the white under base by at least ½ point. This will make it easier to print and can compensate some for ink or shirt shrinkage. So for the most part, the artwork for the white under base is the same as the color to be printed onto it but just slightly smaller in overall size unless your art calls for white outlines. Then you might be printing inside the white under base and following up at the end with a white highlight printer to whiten these areas.
Whether or not you will need to print a white under base will depend on your particular printing situation, inks and artwork. Using high quality inks that may cost more but eliminate the need for a white under base can save a lot of labor costs.
For more detailed instructions and explanations of this process, please see the article link below. This is an awesome article about printing on dark garments by Tom Vann and Charlie Taublieb from impressionsmag.com. © 2009 Nielsen Business Media, Inc.
Printing A White Under Base
Pull Flood And Push Stroke Vs. Push Flood And Pull Stroke
The following is based on manual printing working with textile plastisol inks.
It is very interesting to see how much printers are split on this issue. I learned how to screen print in New York and I had never seen anyone pull their stroke before I moved to Arizona. At first I thought this was a simple case of west coast vs. east coast styles. But that is not the case and it seems this debate has been going on for some time. Only now has it become more an argument of efficiency and ergonomics rather than personal style or preference.
In the early years of my screen printing experiences I was limited to a small group of printers who basically came from a similar “school” of screen printing. As I went to college my exposure to different printing methods was expanded. I took many different types of printing classes throughout my college years but screen printing was always closest to me. It was here that I was being instructed to push my flood and pull my stroke.
I was surprised at this technique, because pulling your flood and pushing the stroke seemed so natural to me. The control you have over the ink is so much better. And the way the ink curls and rolls as you push the squeegee toward the print head just feels right. Not to mention pushing with your palms and controlling the angle of your squeegee this way also gives greater control of the ink.
Now I have tried both methods and there are certain print runs that just don’t work out the best and I end up adapting my flood and stroke methods anyway. But there are definitely benefits to the pull flood and push stroke.
Pull Flood And Push Stroke:
- Much more ink control in the ink well. Ink does not get all over the frame nor does it build up at your end of the screen.
- I believe you can sheer the ink off better with this method giving better coverage and overall print results.
- Using your palms to push is more efficient. It transfers force better.
- You can control the amount of downward force by adjusting your squeegee angle. More of a right angle will force more ink through the mesh.
- Your wrists and fingers will find this method much more comfortable over long print runs. Endurance is greater. You will not tire as easily and it does not abuse your wrists as much.
- The angle of the squeegee against the screen causes the ink to roll toward the print head. With a quick movement of the squeegee handle up with a bit of down force at the end of the stroke will clear excess ink off of the blade and make it easy to rest the squeegee without carrying strings or clumps of ink all over the place.
Push Flood And Pull Stroke:
- Ink gets all over the frame and builds up nearest printer making it necessary to pick up the ink with the squeegee and carry it back to the starting point or plainly pushing the ink back and flooding the screen stencil.
- Flooding your stencil by pushing the ink toward the print head with the screen up, increases the possibility of flooding out the stencil completely thus ruining the next print. You have to be careful not to push too much ink into the stencil on your flood stroke.
- This method is very abusive and damaging to the wrists and fingers. Arthritis and carpel tunnel syndrome are results of such abuse.
- It looks messy and sloppy to others. To me, it almost makes the whole process look more haphazard than anything.
- This style of printing makes it easy to get ink all over your product and shop.
Remember, there will be many who will want to argue with me about this and ultimately it comes down to what works best for YOU. I know I am among a minority of printers who prefer the pull flood and push stroke. Everyone is different and likes to work in their way. As far as the physical, endurance, and print quality benefits; I’ve heard that you can lead an animal to water but you can’t make it drink. To each his own, as it were.
Manual screen printing is riddled with variables and it can often need some finesse. That is why I like to set everything up to start out, the same. I follow all of the same methods until an adaptation is demanded by other factors. Screen printing is first a technical skill and secondly an art.
Printing Wet And Printing With A Flash Cure
The following is based on manual printing working with textile plastisol inks.
The ability to print wet is determined by one factor. That is the artwork. If you can set your artwork up so that all the registration is butt/butt then you should have no problem printing wet. Butt/butt simply means the edges of 2 different printed colors come edge to edge but do not overlap. This could be done with all of the colors including the black printer.
This creates a very low tolerance registration. That is to say that you will need to be able to register your colors precisely. It would probably be a good idea to have micro registration to do this. But printing wet will be faster in the long run.
The amount of ink you lay down with each print is also something to consider when printing wet. The next screen down will “pickup” a certain amount of ink off the shirt from the previous ink printed. So, we want to print an amount that is not going to cause a problem with the pickup factor. Just enough is best as a general standard.
The pickup of ink onto the back of consecutive screens will ultimately, over the duration of the print run, cause the print quality to suffer. It may appear fuzzy or blurry at the edges at some point. This is simply corrected by wiping down the substrate side of all of the screens at certain intervals throughout printing.
There is only one time; I can think of, that you must flash your print before moving to the next no matter what. And that is when you print an under base. An under base is often done when printing colors on dark garments. A layer of white ink is printed under and before all other colors. This allows the colors to stay true and maintain opacity over the dark fabric. When you print an under base, you must flash it before printing the subsequent colors. If you didn’t, you would have a big muddy mess.
Flashing between prints is only done when the artwork has traps or layering that makes it necessary to print ink on top of ink. I think most printers avoid this type of artwork set up because it is slower than printing wet. It can be time consuming and riddled with variables associated with flashing.
Sometimes we might want to set the artwork up so that all the colors print wet and then are flashed before finally printing the black. This may be done for various reasons most often dealing with how the black is supposed to look in the final print. It may be that you want the black to overprint for aesthetic reasons.
Either way, you need to assess your end goals of the print run to decide how to print it. This decision may be weighted on the final print aesthetics desired. It may be that the original art dictates how it will be done anyway but for the most part, you should be able to choose to print wet or with a flash. Remember, artwork is the single most important step to creating an excellent, high quality print. If your artwork is not set up properly for screen printing, not only will the print look bad but the job could be very difficult to print.