Question:

Do I have to have retensionable frames to print four color process?

A Rep at a show said I had to to get good results.

Answer:

Retensionable frames DO make a difference by adding just that much more consistency available to the printer.

Four color process is NOT something magic!

There are many LESS THAN OPTIMUM choices that can help you make a customer happy and even sell more shirts or make more sales.

Hang in there while I go over a few things...

1. Screen printers are as superstitious as a bunch of Medieval bog farmers (or the average baseball player) ...

This is an industry based on facts, equipment and chemicals - sacrificing a chicken to JoBoo will NOT help your printing! On the other hand FUD - Having Fear, Uncertainty, and Doubt about printing (like 4CP) will only limit your shop.

2. Four Color Process is both wonderful and dreadful at the same time - DEPENDING ON YOUR EXPECTATIONS!

If printing a colorful shirt for a customer is the goal (a green is green and a red is red-ish is "good to go" - a beginner step) then using 4CP is a way to make some customers happy and increasing sales.

If you have never used photoshop and want to print a photograph of human faces with subtle colors on a manual press, with loose wood frame screens and low mesh - you may be in for a challenge!

3. Any screen mesh able to hold a reasonable halftone CAN print 4CP - it may not be the OPTIMUM of results but it can print the inks onto a garment.

4. Any press manual or automatic that can hold reasonable registration can print 4CP! Printing 4CP with a manual press will always have inconsistent results because of the lack of control of critical process items like pressure, angle and speed - that does not even take into consideration the substrate issues, ink brand, ink build-up, and all the issues of exposure and emulsion...

5. Professionals in this industry spend entire carriers building the knowledge necessary to attempt to predict and control the variables in this process to produce the most exacting reproduction of colors and tone for 4CP!

6. Because so many screen printers think JoBoo can help them, using simple facts and procedures can help your shop become more advanced in printing and offer what the JoBooists cannot - a more advanced product that can demand higher charges and gain you a reputation you can use to leverage more sales at a higher profit.

7. There will always be some shop or printer better than you are at something! Find what you can do best!

8. Scaring the average printer OUT of a printing CHALLENGE is also COUNTERPRODUCTIVE! (yes I know it happens)... If any of you have seen me printing a 4CP at a show or at my class you know that the jobs were never designed to win contests, but rather prove a concept - 4CP is a useful TOOL for your graphics production!

9. To say that you HAVE to have retensionable screens and an expensive automatic press to print 4CP is as wrong as to say that you can print the best in 4CP work with a wood frame screen, 200 white mesh, SBQ emulsion, laser printed positives, and a crappy manual press!

There is merit on both sides and the answers are based on outlook and desired results - the real answers cannot be given with a five minute phone call but a conversation over equipment that takes HOURS.

Shake off the FUD and give up on JoBoo, buckle down and learn the facts, try the challenges, take the risks and buy what you need for YOUR PARTICULAR RESULTS BASED GOALS.

You can never go wrong looking at the situation with logic and planning - if you need help there are LOTS of folks willing to help you, but you need to have a goal FIRST, and be willing to look at the problem in several ways and with more depth of study...

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.

Chose an ink best for the substrate!

One of the longest running and frequent questions about printing on garments is the issue of fabric with polyester content and the use of plastisol ink.

The simple answer is that no matter how high quality your plastisol or how exotic the additives, there is a chance of "visual color transfer" often called bleeding.

The lower the content and effectiveness of your "blocking" additives and higher percentage of colored polyester content - the higher chance of that fabric color becoming visible in the ink layer. There is no plastisol that I have seen on the market - even the best available that cannot be defeated by even the simplest of red polyester garments.

There are now what seems like endless volumes of FREE information in this industry about the exact physical, temperature, and chemical interactions that cause "bleeding", in it's exact technical terminology but the simple answer is that polyester fabric and plastisol are and can interact because there is a basic chemical "compatibility" with the two products. This compatibility means that when we print plastisol on poly and heat it (as we need to cure it) this process can begin and can be so overwhelming that even the BEST of the "low-bleed" plastisol inks can be defeated. There are several stages involved in this color transfer I encourage you to read some of the excellent information from some of the respected quality Ink companies out there.

There are a few who will tell you that "bleeding" is all your fault, that you are just not keeping control of your heat with the flash or dryer - you only have to keep your heat high enough to cure plastisol and not go over the temp that causes the dyes in poly to start to sublimate (turn to a gas) often this is less than 10 deg. F. !

The other excuse I see is that the garments are of poor quality, and have too much dye, while this may all be true - often you (or your staff) have problems keeping tabs on your heat (like in the real world you never have problems ).

Of course to suggest that you can should only the highest quality fabrics to print or that you should control what garments the customer could order is ridiculous bordering on fallacious. Rather than attempt to cover for the weaknesses in a product why not find a quality alternative.

What to do?

Consider inks OTHER THAN plastisol.

Within a few months, there will be available (widely) on the market an ink that is a "dual-cure" that is formed by heat under 260 deg. F. into a "dry" layer and that within 24-48 hours makes a complete bond with the fabric - a silicone ink.

There are other products that are problematic, fabrics that are not capable of reaching the cure temp of plastisol without damage.

Recently an air dry, time cured ink became available on the market for products that cannot be heated to high temps.

While not as opaque as plastisol, simply lower the temp of your dryer, apply ventilation, this forms a dry layer over the product and the final drying can be in a ventilated area - great for the synthetic bags so popular in the grocrery stores now.

One of the most problematic garments are the athletic "wicking" products, swimsuits, spandex, and other garments that distort in and out of shape, plastisol with even the best "stretch" additive will never be able to stretch as much as the newer silicone inks.

Of course, to create an opaque layer of ink, especially with bright and dark garments the layer of ink is thicker, this can make things uncomfortable for the garment user, while somewhat unavoidable with plastisol as well as the newer inks, good control of deposit with quality screens can make this less uncomfortable, the choice may be a stiff water and air proof layer of stiff plastisol that has a high chance to bleed or a softer flexible coating that can be (but not always) rubber like. With the higher meshes the alternatives often have a softer hand than plastisol.

QCM inks makes the "rubber" but air dry ink, they can be contacted at the following:

QCM
930 Central Avenue South, Kent, Washington 98032 USA
1-800-321-0170
http://www.qcminks.com

Dow Corning is developing the silicone based ink, they can be contacted at the following:

http://www.dowcorning.com/content/textiles/screenprinting.asp

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)...