Knowing about how screen printing worked when twisted multi-fiber thread mesh was common or the only thread available and synthetic threads were new is interesting but new products only hold a basic similarity in performance to that primitive equipment.

A laundry mangle is an interesting tool but knowing how to use one has noting to do with current methods for home clothing washing - compare that to what we have now in screen printing. Talking about chromate emulsions or rope and groove screens has simply become inapplicable history. Anything from the industry 10 or longer years ago is only interesting reference, mesh alone has improved vastly and even retensionable screens have had wonderful changes and additions in the recent years.

I started screen printing many years ago trying to find a way to make airbrushing t-shirt designs faster, I never stopped even when I wanted a "real" job. Of course how long you have been doing something, often wrong, and that would include myself, is not as important as if you listen, communicate and search for new information, you could call that continuous improvement if you like - see it fix it!

If a product works, why live with something that is as harsh on you as carburetor cleaner? Surely some harsher chemicals work faster or even "better" and I present this issue in every class. In fact, in my class we use examples of the mildest soy based chemicals, organic extract based chemicals, and the harshest of petroleum chemicals side by side so the students can see exactly how they work and make the judgement for themselves.

Lots of small shops start off in a building in a retail location with neighbors, and some (where legal) even start in their basement or garage - odor and close neighbors can be a big issue in this industry. I try and help the students understand efficiency in lots of areas, including art, exposure, reclaiming, and where some new products can even eliminate or shorten some steps. Certainly many things are not for every shop, but I like to review as much as is needed. Because I specialize in helping new and small shops I have learned you have to have some mercy and lots of patience.

I even have several sections in my class presentation where I talk about alternative products, how they work, and products that have real equivalents OTC (over the counter) and things that are simply myths or frustrations waiting to happen. In fact we are on the 20th revision of the class with a new workbook filled with custom drawings, micro photos, and information provided by the people who know, study and make the products.

Its not information just to fill pages, our class is filled with facts we have gathered continuously for years. We make continuous changes to the class when new products come out, and new methods emerge. We always look for the next screen printing myth to test - if things change or new facts come up it is immediately in the next class. I have found that if you want to know about emulsion spend time asking the great folk in the labs at the manufacturers factory. If we want to know about inks call a trusted representative then get a sample - find out - and try it out.

On a final note we don't compete with our customers, or students. We are in the industry to educate, and my part is to study screen printing, observe, test products, and work directly on site with shops providing information and troubleshooting. I am not going to manage the day to day operations of a business that would be competition with our students, many who end up as great friends.

I have been criticized for my use of a microscope in the industry, but what is nice about a tool like a microscope is that you can show why things like EOM work and why printed dots that are very small don't print well on t-shirts. A microscope will show how small dots can drop into a thread crevasse. I have found that the microscope gets lots of "ah-ha" moments especially with printers who have done things in an outdated way or with outdated equipment or methods, it shows clearly the limitations with equipment or product and points out the function and limitations of the five basic types of emulsions. In other words it is a great educational tool I like it and will continue to use it to help our students.

Recently there have been several machines capable of applying ink, wax, or other media directly onto a screen's layer of emulsion to replace the positive. Basically everything we need from the positive without the film. More on this later.

Without waxing poetic about the past or pontificating too much lets look at the issue of positives, RIP software, and exposure.

Back many years ago when many of us were foolish enough to think that we could get away with "laser printer" positives, we tried to replace our far superior silver/chemical based film positives. Our camera shots, even the PMT shots had both darker "blacks" (a higher D-Max) and a clearer base film (D-Min) than vellum or the frosted film. We thought that we were saving time and money by shooting toner based positives quickly from a laser printer, we sprayed them with a repackaged artist-fixitive (something that always worked better than hair spray - it was the evaporative solvents that did the "melting" of the toner) and passing the quickly printed vellum to the screen room.

Of course this only cost the "screen room" time and effort - far more than we were saving in the "art room" we were soon forced to shoot paper positives with the old manual cameras to make reasonable positives. This did not last long, and as soon as we were able to justify to the ownership we needed an image-setter, life was good. We had more time for more artists to print more product. Production with excellent positives shot to the roof, and that was when a Harliquin RIP and a VLR image setter with chemical developer was a 48K investment.

In the industry there has always been the old argument over what was more important D-Min or D-Max. the REAL issue is CONTRAST it is not just the clear of the film or just the dark black but BOTH. We want the best of both, simply better is better, high quality always trumps mediocrity.

Discounting the need for a good D-max is showing a basic misunderstanding of how electromagnetic energy or "Light" works and how emulsion is exposed. Light waves never "slow down" - light is light and it either is blocked, bent, (refraction), or filtered. Light continues on - always the same speed - the speed of light. Reaction times change in emulsions based on the volume of light energy.

The lower the D-Max the less light is blocked (more accurately filtered) and the more electromagnetic energy passes through the dark areas. The dark areas of the positive control how much light is filtered, the lower the density/opacity the more light will pass through into the emulsion layer. Regardless of how powerful or fast the exposure the light always is the same speed and any light that passes into the dark areas of the positive and is not filtered continues on to the emulsion and starts the exposure reactions in the emulsion.

Here is an example of a poor black on a positive, even with a ridiculously thin coating of emulsion to compensate by shortening the exposure - it clearly did not work. A correct and full exposure has this and other negative results with a poor positive.

It is always in the facts, the microscope tells all, poor positive, poor results or you are forced to underexpose.

What does this have to do with a RIP?

Inkjet printers without a RIP in front will only deposit a particular pre-determined amount of ink on each dot from the piezo head, this is measured in picoliters (One millionth of a microlitre; 10-12 liters) a very small amount of ink, and that is always set at about 3 to 4 with the free software for the printer.

Epson printers have this setting infinitely variable via the information sent by the printer driver, in other words Epson left their inkjet printers open to performance modification by software.

To modify the inkjet ink deposit you have to have software that will change the ink deposit. The free driver supplied by the manufacturer is designed for ink deposit to give pleasing or accurate color and will be limited in ink deposit volume to about 4 picoliters per dot including the black inks.

With a RIP the printer is "told" to "squirt" enough ink to fulfill the demands of the user, and the RIP makes this much easier to adjust often with settings from 6 picoliters to 27 picoliters or more per machine dot printed - that is each machine printed dot not the formed "dots" you would adjust as "LPI/frequentcy" in your vector or raster program. Contrary to assumptions a RIP not only converts the image but tells the printer EXACTLY WHERE (so it holds registration) to put a dot and HOW MUCH INK to deposit.

With a thin, poor black as the dark areas (D-Max) the black becomes like the darker areas of an exposure calculator - not dark enough to block or filter all of the light energy and some of the emulsion is exposed behind the black, the more full and complete the exposure the more the open areas under the black are exposed leaving remnants after wash development and forcing the user to "blast" the open areas excessively leaving ragged edges.

With the poor covering of ink from the standard driver you do not create a black that will block sufficient light to keep the emulsion from forming a skin of slightly exposed emulsion over the face side UNDER THE BLACK. To then open the stencil we would have to put enough pressure on the open areas in wash development to "break" the edges of this "skin" off and that will result in an edge that is rough and will present a less than desirable printing "gasket edge" against the product.

Professionals use professional tools, using a RIP has other advantages, the biggest one in art production is using the graphic tools we have correctly. No real graphics professional wants to go back to breaking jobs up and fidgeting with photoshop to get dots or separations, directions for this procedure you can find on the internet for free, but the results are a poor D-Max and the resulting problems.

Postscript a beautiful thing, no serious artist is going to go back to the days before the introduction of Adobe separator (a program that is now imbedded inside of Illustrator and has been for over a decade).

Not using good quality film, quality inks, and a good adjustable RIP, a printer cannot get the real and required contrast from D-Min to D-Max to get positives that will allow professional results with full and complete exposure. The combination of special film for positives, ink designed for positives, and an adjustable RIP are the tripod of good positives with an inexpensive inkjet.

How to START to chose a line count (frequency) correctly for your mesh

There are simple answers and propeller head math junkie answers.

Unless I am mistaken you can find a rather complicated formula for finding exact (yet theoretical) size to mesh relationship.

I tell new people that they can start at 5.5 factors.

230 divided by 5.5 - 41.81 - I start with 42 most of the time.
305 divided by 5.5 - 55.45 - I start with 52

Reverse also - I have to have this broken into dots that are 36 LPI (frequency) so...

36 multiplied by 5.5 - giving 198 so to get the maximum theoretical ink volume (highest opacity by thickest deposit of ink) I can use a 196 to 200 mesh.

This is ONLY a SIMPLE starting point - for advanced users you have to consider emulsion choice (and it's ability to hold detail and bridge well), EOM and your particular mesh.

The best way is to start with a simple and easy idea and build on that with testing.

You can make positive strips with halftones of various LPI on each strip, shoot for your full and correct exposure and develop and print the various sizes with both dark ink on light backgrounds and white ink on dark background and save the results for your art development and choices for mesh and available detail.

Good EOM...

Coating Screens for Maximum Effect

Full Exposure, Pressure washer develop (step wedge/exposure calculator)

Exposure Control

Tight screen tension (you have with retensionables)

Quality emulsion, most diazo dual cure emulsions are favored for the ability to image great detail.

I also favor larger dots than you mention (40 to 45 on "230" and 62 (when by itself) for an angle (note this is a STARTING POINT).

Did I mention a good positive?

That requires a good printer, good film, god ink, and a RIP - unless you are using an I jet or Oyo film or DTS...

Before I start into a rant, I want to talk about coating screens, a key in good halftone dot formation on a photo stencil.

Using my preferred method to coat screens they are most likely to be much thicker than the norm, about 5-20 EOM (this is recommended by the emulsion and ink companies for good edge definition and bridging).

5 to 20 percent EOM is 3 to 20 times thicker than most screen printers apply (Im not even talking about Cap films yet).

Nothing short of reasonable quality film and good opaque darks will allow a FULL exposure! I have NEVER had output from a laser printer (yes even that boat anchor Xante) or unaided ink-jet be dark enough with enough contrast to shoot a FULL exposure without problems. I have used the best and the worst products in my own shops, and helping client shops and can tell you this is universal with the products we all use.

Let's not forget the average screen printer... atempting to use a "free" RIP - Using Ghostscript, writing even simple code, and lots of "tweaking" just adds a layer of challenge that makes for THOUSANDS of dollars worth of time and frustration for an already challenging skill development!

Registration...

Yes registration is an issue, traps and tricks may be typical SOP, but a good press capable of close micro (and able to hold position for the entire job) can have any competent printer up and printing faster without excessive flashing.

Use art designed to eliminate excessive flashing, most screen printers flash too much and that is proven by the constant overflow of questions about why 110 mesh is not the best for everything, 110 mesh range should be your LEAST used mesh.

NO 110 mesh is not good for four color process.

Professional or skilled/master craftsmen?

In the construction industries there is a term used "jack-leg" to denote a person or business operating and selling services without the required skills, supplies or equipment. Jack-leg also often denotes a lower quality product. Have you ever wondered why our industry has such a bad reputation for "hacks" or "jack-legging"?

To be a professional or skilled craftsman in business also requires an ability to study, improve and increase efficiency and profits.

Using a good positive with an opaque layer in high contrast to the carrier plastic will provide:

a. the ability to coat higher quality screens with good EOM
b. the ability to expose the stencil fully
c. fully exposed screens last longer
d. fully exposed screens wash faster and with greater quality edge
e. a high quality stencil will print with better definition, edge quality and detail
f. close registration will increase the general production speed by using fewer flashes
g. fully exposed screens reclaim faster and with less chemicals

All of this from the start with a good quality positive (hopefully with good art behind that)...