Screen Printing Articles Industry Alert Hot Shots Photo Gallery Message Boards Visit Our Advertisers: 3M Commercial Graphics Advance Corp.- Braille Tac Div. ArtCAM CADlink Technology Clarke Systems Cyrious Software Estimate Software International Sign Assoc. JetUSA American RENOLIT Corp SGIA Specialty Graphics Imaging Assoc Supply 55, Inc. US Banner Corp USSC- Sign World USA

How many times can a screen be reclaimed? That depends on the condition of the mesh, which can be the result of many factors that are far removed from the reclaiming process. How carefully has the screen been handled in the shop? How long were the print runs it was used for? What type of ink was used? What kind of substrate was printed? What was the condition of other equipment that has come into contact with the mesh: scoop coaters, squeegees, and floodbars?

Printing undoubtedly produces the greatest amount of wear and tear on a screen, but the reclaiming process comes in a close second. During reclaiming the mesh in a screen is attacked with harsh chemicals and high-pressure sprays, a lot of abuse for fragile threads only a few microns thick.

Many screens fall victim to ill-advised attempts to cut corners, such as using off-the-shelf products from the local home improvement store rather than chemicals specifically designed for reclaiming screens. Another example of false economy is the failure to buy proper equipment. A reliable pressure washer with an output of at least 1200 PSI is the one piece of equipment you absolutely cannot do without. Still, people will try anything to avoid buying one, including bundling up their screens and hauling them off to the local car wash.

Cutting corners in screen reclaiming often ends up costing you more in shortened lifespans for your screens and increased labor costs because they simply take longer to do the job. So to save yourself money and get your screens safely through the reclaiming process your first step is to make sure you have what you need to do the job, or rather jobs at hand.

Let's take a look at what is involved in screen reclaiming. It really breaks down into three separate tasks:

Cleaning the ink from the screen.
1. Removing the stencil from the mesh. (Sometimes called decoating.)
2. Dehazing, or removing any staining or ink residue that might remain.

The equipment for job number one is about as simple as screenprinting equipment gets. You need something to lift the greater portion of the leftover ink out of the screen. The one essential requirement is that it has edges that won't damage the mesh. Screenprinters have used palette knives, paddle-like spreaders from restaurant supply houses, credit card-sized squares of plastic, or the plastic squeegees used to apply cut-vinyl sign material.

If a screen is to be kept in inventory against future reprints, the clean-up process would be much more involved. With a screen headed for reclaiming, you don't need to worry about removing all of the ink. In any event, clean-up of the screen should begin as soon as possible after the last print has been pulled. The longer you put it off, the harder it's going to be. This is especially true of air-dry inks. If reclaiming is going to be postponed you need to clean all the ink from the screen just as if it were going into inventory.

Now let's take a look at the supplies and equipment you need for the rest of the reclaiming process. Equipment and Supplies for Reclaiming Screens

1. Reliable water supply and drainage.
2. A power washer.
3. Reclaiming tank. (Most shops use the same tank for reclaiming and washing out screens after exposure.)
4. Miscellaneous brushes, hoses and nozzles.
5. Personal protection: eye protection, waterproof aprons, rubber gloves.
6. Reclaiming chemicals:

• Ink remover
• Stencil remover
• Dehazing compound

Water supply
Reclaiming uses a substantial amount of water. Opinions differ about whether a hot water supply is necessary, but you can definitely get by with cold water alone. Some printers feel that a warm water spray speeds stencil removal, but it can also make some types of blockout more difficult to remove. Cold water is always safe.

Drain
Today, thanks mainly to environmental regulations that affect what you may or may not put down the drain, getting rid of the water afterwards can pose more of a problem. Many screenprinting suppliers advertise their reclaiming products as being "drain safe." This simply means they consist of chemicals unlikely to cause environmental harm when they enter the sewer system.

This is a good reason for purchasing reclaiming chemicals from a regular industry supplier. But across this country many different state and local environmental rules affect wastewater disposal, so you really need to know what the regulations are in your area. Some localities may require special methods of dealing with the contaminated wastewater issuing from your tank. In others, you may be required to have a closed system to isolate and recycle your wastewater. A closed system or some sort of filtering system may be a necessity if you are on a septic system; some reclaiming chemicals can damage or block it.

The area near the reclaiming tank tends to be one of the messiest places in the shop. Shelves hold a variety of reclaiming chemicals. Note the two pressure washers. One serves as a backup in this busy facility.

Pressure Washer
Stencil removers can do a good job of breaking down and loosening the stencil, but they simply can't do their job properly without the assistance of a power washer. The same thing is true of dehazing products. Fortunately pressure washers (also called power washers) are available at almost every hardware store and at fairly affordable prices. Buy the best you can afford and look for one that will stand up to rugged use. A pressure washer in an average screenprinting shop will be switched on many times a day. Pay attention to warranties. You may need to use them.

Since your pressure washer will be used indoors, you need an electrically powered type. As far as amperage is concerned: the higher the better. As a minimum you need a pressure washer capable of delivering at least 1200 PSI. Studies suggest that screens can endure pressures up to 4000 PSI without sustaining damage.

Pressure washers come in both hot and cold water types. The cold water types are cheaper and generally better for reclaiming purposes. Manufacturers often supply figures for water flow in gallons per minute (GPM) and, sometimes, cleaning units (CU) (pressure multiplied by water flow), but PSI remains the most useful figure for comparing pressures washers to be used for reclaiming. Make sure that the unit has an adjustable nozzle. The ability to direct a tight spray at a stubborn bit of stencil clinging to the mesh comes in very handy.

Wash tank
Some shops make do with nothing more than a concrete block wall to lean their screens against and a floor drain. But when you shoot a high-pressure spray of water against a hard surface it's going to bounce back, usually in every possible direction but mostly at you. At times this backspray will carry significant amounts reclaiming chemicals, including harsh caustics like potassium hydroxide or sodium hydroxide, often used in the dehazing process.

That backspray, unless you have some means of controlling it, can travel quite a distance in your shop. The ideal means of controlling is a wash tank, also called a wash sink or a washout booth, essentially a shallow box resting on one of its narrow sides. One of its wide sides is open except for a raised lip extending a foot or more up from the bottom. The bottom of the tank generally slopes in the direction of the drain, and it should be wide enough to allow screens to be leaned against the back wall. If a screen isn't securely placed when you hit it with the pressure spray the powerful blast of water can send it flying. The drain opening should be protected with a strainer to block bits of debris that could clog your sewer. And if you're located in an area where environmental regulations require it, the drain should be hooked up to a waste processing system.

Wash tanks are made of galvanized or stainless steel or chemically resistant polypropylene. One of the most useful features manufacturers have come up with is a backlit panel that forms the back wall of the tank. This allows you to view the mesh against a light source, making it easy to spot blocked or damaged areas. It is equally useful for reclaiming and for washing out stencils after exposure. Most wash tanks serve this double purpose.

Don’t scrimp on size when buying a wash tank. You may someday be printing with larger screens and it's easier and more economical to buy a larger one in the first place than to have to upgrade later. It should be placed in the shop away from anything that could be damaged by backspray, especially screens ready to go onto the press or to be kept in inventory with the stencil intact.

Brushes
You need brushes for applying the chemicals to the screen. Some people use sponges, which may be better for using liquid-based reclaiming products. Brushes work especially well with products that come in the form of a gel or paste. Take care that the bristles are soft; hard bristles can scratch the mesh. Ideally, you’ll use separate brushes for ink degraders, stencil removers, and dehazing products. Try not to mix them up, and after you use them, brushes should be rinsed with water to remove any chemical residue. You don't want reclaiming chemicals drying on the bristles and making them stiff.

Spray Bottles
Pump sprays are ideal for applying liquid reclaiming products to your screens. They can save you money by allowing you to control the amount of chemical applied, so that very little ends up being wasted. They also allow you to direct the chemical to the area where it's needed.

Garden Hose
In reclaiming, the pressure washer does the lion's share of the work, but it's also helpful to have a hose to deliver a stream of low-pressure water to rinse the last bits of stencil and reclaiming chemicals from your screen. For this purpose volume is more useful than pressure. Backspray from a pressure washer can often cause chemicals and bits of old stencil to bounce off the back of your wash tank onto your screen. When rinsing screens, pay particular attention to the inside, at the juncture where the mesh attaches to the frame. Gunk tends to accumulate there.

Personal Protection
No one wants a face full of chemicals, especially if you're going to be dealing with some of the caustic chemicals in the dehazing process. Be sure whoever is doing the reclaiming is wearing adequate protective gear. An acrylic face mask and rubber gloves that come well up the forearm are the minimal amount of equipment you should consider. A rubber apron is also a good idea. Caustic chemicals can eat holes right through fabric, not to mention skin. Make sure you have MSDS (Material Safety Data Sheets) available for every chemical used in your shop. And just don't have them available, but be sure that everyone who works with them has read and understood them. This is a legal requirement in any case, fortunately one that is easy to comply with. Whenever you order a new chemical, get in the habit of automatically requesting the appropriate MSDS sheets from your supplier.

When you are buying protective gear, buy heavy-duty equipment. It not only protects you better, but lasts longer. For example, when buying rubber gloves invest in industrial-strength types, not the kind designed for household use. Some printers also use facemasks with air filtration. When a pressure-washer blasts dehazer out of a screen it’s easy for the air surrounding the wash tank to become saturated with a mist containing caustic chemicals, which is very unpleasant to breathe.

Chemicals
You need three chemicals to reclaim screens. The first is an ink degrader, a product designed to break down any ink remaining in the screen. Depending on the type of ink degrader, it can either be used alone or in conjunction with the stencil remover. The stencil remover is, of course, the second necessary chemical and its function is self-explanatory. Not every stencil remover will work with every product. Indirect films, for example, are usually gelatin-based and may require a specialized stencil remover.

The third chemical is dehazer. This is usually a caustic material, which is, fortunately, not required every time you reclaim a screen.

The dehazer’s job is to remove ghost images, stains and telltale outlines of former print jobs formed by tiny fragments of ink embedded in the weave of the mesh. The mesh openings may be clear but these faint outlines remain. Depending on the fineness of the mesh and the kind of detail required in your next print job, ghost images can be ignored until they build up to a point where they begin to interfere with the process of exposing a new stencil. That's when you need to haul out the heavy artillery, your dehazer. This is the one you want to be careful of. Many of the popular dehazers on the market are caustic-based potassium hydroxide or sodium hydroxide (lye and soda ash).

So, now you’ve got your reclaiming equipment. Next time, we’ll show you how to put it to work.