SCREEN PRINTING

Most people starting out spend too much money. If you are new to screen printing, the risk is you will buy what you do not need or more than you need.

Local businesses and schools usually do not request more than two colors. They may not have the need or want to pay for more colors.

The orders requiring more colors or lots of shirts, or items that would be a new printing problem can be sub-contracted to another screen printer. That allows a person with limited funds to start a business without spending a lot of money on capability that will seldom be used.

The dryer can be a flash dryer rather than a faster conveyor. An exposure unit can be made at home for under $50 to avoid spending $1200 and more. People starting out do not need a lot of money to offer excellent quality to customers.

The starting point for a new business is a realistic assessment of who the customers will be, and what they will need. Keep it simple. Planning to print T-shirts and one other item at first, like tote bags, will make starting a new business a more pleasurable, productive and profitable experience. Too many different items to print can create too many problems for an inexperienced screen printer.

Training Before spending any money, get training. Screen printing involves many cross roads at which you will make decisions. Will you go in the right direction? For example, there are several types of wooden screens, welded aluminum and retensionable screens. There are diazo, dual cure and photopolymer liquid emulsions and capillary films. That is just the beginning to the number of choices, and each requires training.

People starting out typically select the lowest purchase cost, and do not consider the ownership costs. If one screen costs $16 and another $35, but the $16 will produce some misprinted shirts, slower production and aching wrists, is the $16 screen the better buy? Most people never ask the right questions.

Training is available from many sources. There are books, schools, seminars at trade shows, trade magazines, audio and video tapes, and people who will help you. You might even take a job working for another screen printer before starting out on your own. During this process the choices of products and technology should be itemized and evaluated. The risk is, being new, you might not know the right questions to ask. What might seem like the best option might not be the best option. Mistakes can be costly, and may ultimately require investment a second time in a type of product that has already been purchased.

To a large extent, a person new in business relies on what sales personnel and screen printers suggest. To make sure you are taking advice from a major league player and not a career minor leaguer, the work of the mentor should be inspected and critiqued. There are lots of sales people who have never printed.

Many screen printers have not taken the time and spent the money to itemize and evaluate the choices. When offered a satisfied customer list, consider the source. Anyone can produce such a list. Even cold calling screen printers in the Yellow Pages does not establish whether the person answering the phone is a major league player.

You need to see the advisor in action to know if you have the best source of information. Trade shows, shop visits and published accomplishments are good ways to evaluate the person whose advice you will be relying upon. Their advice is a form of training.

Training reduces risks. Unfortunately most people start out without any training. Too many get frustrated and give up on their dream of having their own business.

Press Selection Most people starting out think more colors are better. Actually, more colors on a manual press result in lower productivity.

For each one foot increase in the diameter of a press, the person printing will have to push the screens around in a circle an extra 3.14 feet per shirt. That is because the circumference of a circle is measured as diameter times Pi (3.14). Selecting a 6-color press with an 8 diameter rather than a 4-color with a 3 diameter adds 5 x 3.14 or 15.7 of movement per shirt, or 1570 for 100 shirts.

That machine will be the foundation to the print. The foundation needs to be rock solid. If the platen or color arm in the registration gate move during printing, printed images may be out-of-registration. Push down on the platen with the force used when printing. Does the platen deflect at all? If it does, find another that does not deflect.

When the color arm is in the registration gate without a screen, an attempt should be made to move the arm laterally and to twist the arm. There will be zero movement of platens and color arms on the best presses. Larger diameter presses are more difficult to design without deflection, because the force you apply is being leveraged over a longer distance.

People often ask about the difference between a press with one platen versus four or six platens that rotate independently from the screens. If your business will involve a lot of flash curing, the rotary press will be more efficient. A rotary press or platen is sometimes referred to as a speed table. A press with a speed table requires more space and costs more money than a press without this feature. The question, then, is whether or not a flash is necessary.

A lot of flashing may be unnecessary. For example, if screens are very tight, a lot of printing can be wet-on-wet. That means successive colors are printed without flash curing. The color of the garment, mesh count, type of ink and choice of liquid versus capillary film bear on the answer whether flash curing will be necessary.

There are all those cross roads in the decision making process again. If the customers are businesses and schools requiring typically two color images rather than retail store customers who want 6 colors, the cost of a speed table can be avoided. The cost of lower productivity from flash curing on a few jobs may be better than a larger, less productive, press on all jobs.

Micro registration is a key feature to be considered. The image in the screen is exposed from a positive. A positive is a black image on clear or transparent medium like vellum. The positive is taped to the platen and the screen is moved until its image matches the positive from which the screen was made, exactly. When tightening the screen in the press, often the screen will move slightly, especially if the screen is over tightened.

Rather than loosen the screen, the micro is unlocked and micrometer-like fine adjustments can be made. That is micro registration in theory. In practice, a micro may move a screen over a curved line or along a straight line. A curved line is almost impossible to work with, but the more common situation, particularly if you buy an older, used press. This is a feature to see demonstrated, but only an issue if printing a lot of jobs more than two colors where the colors are butt registered or four color process.

There are many other features in a press to examine. What is the range in size and weight of screens the press can accommodate without screens flying up or falling down? What attachments are available to expand revenue? How fast can an attachment be changed? Are there knobs or press structure for wet shirts to catch on and smear when the shirt is being removed? Doing your home work is important to getting the most value for your investment.

Dryer Flash dryers cost less and take less space than a conveyor, and can be used for a full cure. A flash cure is typically 6-8 seconds whereas a full cure is 60 seconds.

A flash cure prevents the ink from picking up under subsequent screens during the printing process, but does not cure ink sufficiently for ink to survive repeated washings. Sometimes flashing is necessary. Dark shirts with a very soft feel, or hand, often have been printed with a very thin coat of white ink, known as an underbase, flash cured, and then over-printed with the same or different color. Materials that do not absorb ink like nylon jackets must be flashed before printing the first color and between each color so shrinkage occurs before printing and inks are not smeared by subsequent screens.

The problems with using a flash unit for a full cure are low productivity and stress you suffer worrying about the cure. At best you can fully cure 30-40 shirts per hour with a flash unit compared to 100-150 and more with a conveyor dryer. A conveyor runs at a constant speed and temperature giving a consistent result. The stress that comes with a flash unit is the concern too short of a cure time will create unhappy customers when the ink washes out. Too long of a flash will scorch the shirt. The margin between too short and too long is very thin. Monitoring the cure time while trying to load and print other shirts creates stress. The solution is slow curing and low productivity.

When selecting a flash or conveyor, look first for a temperature control. A household iron has temperature control to regulate heat for 100% cotton versus synthetics. Heat control is a must, but many dryers do not include this requirement.

Check flash dryers to see if they are top heavy and subject to tipping over with an element at 350 degrees. Check for legs that stick out for someone to trip into the hot element rather than a stand positioned out of the way. The element must be absolutely parallel to the platen for puff inks to puff evenly. You might want casters on a flash unit for your convenience.

A flash unit in smaller shops will be 110 volts so it can be plugged into any electrical outlet. Outlets are designed for a maximum of 15 amps. Some flash units will draw 19 amps. Excessive amps in a circuit can cause a house fire. A plug with two parallel bars is designed for a maximum of 15 amps whereas one bar perpendicular to the other bar is designed for 20 amps.

Heat for curing comes from wattage. Watts are volts times amps. A 220 volt unit will produce the same wattage as a 110 volt unit that draws twice as many amps. A new shop can buy more curing capability by specifying 220 volts. The circuits, switches, etc., in the dryer will last longer with lower amps and higher voltage like 220, 230 or 240 volts. Gas as a replacement for electricity only makes economic sense in larger dryers.

Flash dryers and conveyors without vents bake the ink whereas conveyors with vents have substantial convection. A conveyor without a vent, or which has a covered vent, runs much hotter, because less heat escapes. That is acceptable on a lot of jobs, but dark shirts being cured in a conveyor can create an odor you won t want to smell all day. The choices will be a vented dryer, or open the windows and doors.

You never want to find lint on shop surfaces, because that means you are breathing lint which gets lodged in your sinuses. Adequate draft in a vent makes a dryer less efficient, but the work environment healthier. Lint in sinuses causes headaches. I learned this when I was unable to work for five weeks after printing 100% cotton shirts two consecutive nights in a 25,000 sq. foot room without venting.

Screens Every screen printer with 20 minutes or more experience pulling a squeegee agrees tighter screens are better. When a screen is tight one color is less likely to bleed into another color. Half tones will be reproduced more accurately rather than be dragged across the shirt. Ink can be cut easier and more cleanly. There will be less chance of ink build up under a screen and more chance of a brighter, softer image in the garment.

All mesh relaxes. Higher mesh counts like a 230 or 305 threads per linear inch composed of 35 micron diameter threads will lose 25% of its tension within two hours of being tensioned close to its breaking point. Lower mesh counts lose tension more slowly. Often screen printers receive what they think are tight screens which they recognize as being softer at the end of the first print run of 100 shirts or more.

The solution is to retension mesh after two hours, then four hours, and the next day before using the screen on the first job. When the job is over, remove the ink and stencil, and retension after each job until 500 prints have been accumulated on the mesh. At about this point, the mesh becomes work hardened, and will not need further retensionings. Jobs will be easier and faster to set up, but more importantly, image quality will be far superior.

At a trade show, observe what kind of screens the press manufacturers are using, and their image quality. Find out what the large contract printers use. Then find out if your advisor is major or minor league by the screen recommended.

Emulsion Liquid emulsion should be applied with a scoop coater devoid of any nicks. The angle, speed and pressure applied during the coating process affect the stencil thickness. Other variables to stencil thickness are the number of times the scoop coater is drawn up each side of the screen, air temperature and humidity. Capillary film avoids all these variables as long as the person coating the screen does not squeegee the wet, soft stencil material into the mesh.

Capillary film is fundamentally different from liquid emulsion. With film, the ink passes around the threads of the mesh and the image is created by pure stencil material. The image resolution will be better when the mesh is not in the stencil influencing how the image is created. That is another reason not to squeegee wet capillary film into mesh. The film thickness controls the thickness of the ink deposit and therefore color. With liquid emulsion, the mesh count meters the amount of ink passing through to the shirt.

Capillary film avoids production losses from pin holes and provides other benefits, but most of the screen printers (the people you might ask for advice and training) use liquid rather than capillary film. Most of these folks have not itemized and evaluated the choices in emulsion versus capillary film, or did so before the newer, better formulas were developed. Liquid emulsion is fine for start up shops for non-critical work, short run jobs with large images in multiple colors, and when you have time to fix pin holes in screens.

Ink The ink companies all know each other s prices. When you realize that you can print say 300-1000 shirts per quart, a dollar or two difference works out to $ .006 - $ .002 difference in cost per shirt. Performance is the issue, not price.

Inks are the most difficult part of the screen printing process to understand. The ink companies worry about how their colors match to independent standards so your image meets your customer s requirements. Suppliers talk about viscosity which is a statement about flow. An ink most screen printers favor is viewed as creamy.

Too much flow can result in dot gain. That is ink that spreads out on the garment. The ink deposit might get thinner losing color strength or sink into the garment allowing the color of the garment to influence our recognition of color.

Inks should be stirred well before being removed from the container. When stirring, pull the stir stick straight out of the container. Does the ink drop off like yogurt would, or remain attached to the ink in the container like a string when the stick is 6 above the container? Now we are talking about shear. Shear is seldom mentioned by suppliers, but is a critical performance characteristic to image resolution, color strength and the feel of the printed image.

Conclusion Starting a screen printing business means confronting the cross roads to your success over and over again. Your largest investment will be your time and wisdom to select the right advisors.

I am always amazed at trade shows and on telephone calls when people only ask price. Only twice in 22 years have I been asked the right question. Ask why you should buy a product and not other products. Ask why you should buy from the sales person and not the competitors. Find out how the competitors answer the same question. Then find independent evidence of who was right.

That will put you on the right road to success.

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