Discharge Ink & Discharge Screen Printing How It Works

Water Base Discharge Inks

Discharge printing can be a valuable addition to your operation. Discharge is not a use-it-and-forget-it product. Discharge printing comes with safety precautions, issues with finished goods, and procedures for a healthy shop environment. These issues are not that difficult to deal with and cannot be ignored. Be prepared to properly handle the discharge products or don’t even try them.

Methods of using discharge

Discharge inks require an activator/catalyst to work; there are two different systems available. The predominant system relies on active ingredient Zinc-Formaldehyde-Sulfoxylate (ZFS). The newer, and less used system relies on Thiourea Dioxide as its active ingredient. There are different name determinations dependant on what the ink company calls it, in most cases formaldehyde is the active ingredient. In both systems, the ink has a limited discharge life once the activator is added. There are two methods of discharge printing, both systems can be used.

1.       The first and most traditional printing method is to discharge every color in the print; there is no need for an underbase screen. This method saves a screen and does away with flashing between colors. The exception to this rule is when a black-ink screen is needed. There’s no need to use discharge if the black will cover without it. When printing on black, any black that is on the design is reversed, that part of the design will use the shirt color itself.

2.       The second method is to use discharge strictly as an underbase. With this method, you can use either white discharge or natural discharge, which contains no pigment and reveals the natural color of the fabric. The following colors are printed with regular plastisol with or without flashing.  Some prefer not to flash the discharge underbase. This saves the head used for the flash and any cool down heads. The end result is that printers can increase the amount of colors they can print on dark shirts by one or two.

The undwhite discharge erbase works well for most design types, especially spot-color work. Even though the other colors are printed using plastisol, the overall print has a less heavy feel because the underbase is a water-based product. If a design contains halftones or other areas with very thin ink deposits, then a natural discharge would work much better. The pigment in the white discharge underbase might mix with the process inks and shift their color. This is usually a problem with spot colors.

Discharge ink underbasing makes true 4 color process printing on dark fabrics possible. For process printing do not use a white discharge underbase. When the white pigment mixes with the transparent process inks, they will turn pastel and muted. Work with a natural discharge underbase that will reveal the natural cotton background color using a highlight white to make the design pop. Process-ink systems can be beefed up using triple-strength versions to compensate for the natural background thus overcoming the off-white background color. Again if the design contains any white color of its own, print a white highlight that is designed to print with the process inks using this application.

Safety issues in production

 

Water-based ZFS-activated discharge is the most used and the most versatile method of discharge printing. ZFS has an unpleasant odor and should be handled carefully in its crystal form then blended into the ink by a properly trained employee. Always blend the ZFS slowly until it is well mixed in the ink to prevent dust, ZFS is relatively safe once in solution. Formaldehyde is a skin irritant. Proper procedure dictates dryers should be properly vented, never use an unvented dryer for discharge curing. Shirts printed with ZFS discharge have measurable levels of formaldehyde. Garments that are allowed to sit for a time after printing in an unconfined state will disperse most of the formaldehyde within days. If at all possible, avoid folding and packing ZFS-discharged garments immediately after printing.

 

Water-based Thiourea dioxide discharge should also be handled with care; it’s a strong oxidizer that must be kept in a sealed container. The same precautions that are recommended for ZFS apply to Thiourea dioxide as both are strong oxidizers to be kept in sealed containers. Efforts should be made to minimize dust when pouring the crystalline powder into the mixing container, occasional direct contact is not considered an immediate health threat but advisable to avoid excessive contact.

Screen printing hands on – the Tradeshow

Hey Everyone. So sometimes you can do all the research in the world over the internet but it just doesn’t take the place of real hands on experience. If you’re thinking about screen printing you might want to consider going to one of the textile trade shows that come your way. It’s a great way to check out different vendors and really educate yourself about the screen printing industry. These trade shows, often with different names, and sometimes covering slightly different aspects of the industry, pop up all over the country.

Here’s a pretty cool video to give you a look at a booth at a trade show.

Is now a good time to start a new business?

There’s almost endless coverage of the recession these days.  Has it affected you?  I’m always curious about that.  I often wonder how much of it is media hype and how much of it is real.  But none the less how does it affect screen printers and their business?  Because it’s a “recession” does that mean you should be wary of starting a screen printing business?  You might be surprised.  Here, check this video out for some interesting answers to these questions.

Sublimation

Sublimation isn’t something we’ve touched on too much in this blog (by the way, sorry for the lapse between posts) but here’s a video that’s pretty interesting.

Info about creating films for exposing your art

Why an Inkjet to Output Films?
The concept behind inkjets will be familiar to most readers: ink gets squirted out of nozzles located within the print head, which distribute the ink across the page as it is fed through the printer. It’s less well known, though, that the technology itself can be broken down into two common types: thermal and piezo.
Although both distribute ink in a similar fashion, the difference lies in how they transfer the ink to the page. In thermal inkjets, the nozzles located inside the print head are heated to create a vapor bubble which forces a droplet of ink onto the paper. Due to the nature of the ink transferal method, many manufacturers refer to these types of inkjet printers as bubble jets. Manufactures producing bubble jets include HP, Canon and Lexmark.
In contrast, piezo printers squirt pressurized ink through the nozzles by charging the piezo crystal located behind the nozzles in the print head with electricity. Piezo crystals vibrate when charged with electricity and this, in turn, pulls and then pushes the ink within the nozzle. By varying the strength of the electrical charges, the technology causes different-sized ink droplets to break away from the nozzle. Also called the vibration method, the technology was patented by Epson and is consequently used in its range of inkjet printers.
FastRIP™
This is a PostScript interpreter called a Raster Image Processor or RIP. Without PostScript it is impossible to print high-quality halftone dots on a “non-PostScript” inkjet printer such as an Epson 2200 or 4000. Even if your printer has PostScript, it may not be able to print halftone dots because PostScript is often just used to calibrate and balance colors on an inkjet. The Epson “RIP” does not print halftone dots! FastRIP™ does!

Plotters
A plotter is a vector graphics printing device that connects to a computer. Plotters print or cut their output by moving a pen/knife across the surface of a piece of paper or film. This means that plotters are restricted to line art, rather than raster graphics as with other printers. They can draw complex line art, including text, but do so very slowly because of the mechanical movement of the pen/knife. (Plotters are incapable of creating a solid region of color by pen)
When computer memory was very expensive, and processor power was very slow, this was often the fastest way to produce color high-resolution vector-based artwork, or very large drawings efficiently. Plotters coupled with a hand-cut water soluble film that is weeded out in a negative form after cutting then applied to a screen, this is but one option to a printer that’s already doing vinyl signs.

In addition to this blog you can learn more info about screen printing here as well as sign up to take a comprehensive class about screen printing and get one on one instruction and learn from the pros.

Introduction to art terms

JPEG

The term actually stands for “Joint Photographic Experts Group,” because that is the name of the committee that developed the format. But you don’t have to remember that because even computer nerds will think you’re weird if you mention what JPEG stands for. Instead, remember that a JPEG is a compressed image file format. JPEG images are not limited to a certain amount of color, like GIF images are. Therefore, the JPEG format is best for compressing photographic images. So if you see a large, colorful image on the Web, it is most likely a JPEG file.

While JPEG images can contain colorful, high-resolution image data, it is a lossy format, which means some quality is lost when the image is compressed. If the image is compressed too much, the graphics become noticeably “blocky” and some of the detail is lost. Like GIFs, JPEGs are cross platform, meaning the same file will look the same on both a Mac and PC.

GIF

Both GIF and JPEG images are widely used on the Web and are supported by all Web browsers and other Web software. The choice is usually a simple one. Charts, screen shots and technical drawings are compressed best as GIFs, and GIFs only hold up to 256 colors (8-bit color). Most all photographs are better as a JPEG, which supports 24-bit color and has the option of several compression levels (the choice depends on how much degradation you can tolerate). If you save a scanned image in both formats, you may see a dramatic difference in file size between them.

BMP

BMP (short for bitmap) is a graphic format used internally by the Microsoft Windows graphics subsystem, and used commonly as a simple graphics file format on that platform. BMP files are usually not compressed, so they are typically much larger than compressed image file formats such as JPEG or PNG. Despite its shortcomings, the simplicity of BMP and its widespread use in Microsoft Windows and elsewhere, as well as the fact that this format is well-documented and free of patents, makes it a very common format. As such, many image programs are likely to be able to read in BMP files.

SPOT COLORS

A spot color is a specially mixed ink that is applied on the printing press, as opposed to a mix of the four inks which make up process printing. Spot colors can be produced in a much more vibrant range of colors, and can have special characteristics which aren’t available in process inks, such as day-glow or metallic ink. Because they only use one screen, spot colors can reduce the cost of printing if you limit your ink choices to black and one spot color. For example, if you choose to print a red and black logo in process inks, you will actually need three inks on three screens (with associated , etc): Magenta, Yellow, and Black.

However, if you are already printing a full-color piece, adding a spot color will dramatically increase the cost of printing. You will add one more color to the four colors needed to produce, for example color photographs. It then is a five-color job requiring five inks, five screens, five positives, etc. Many companies make spot colors, but the most popular is Pantone, Inc. They not only make and sell inks, but they have a process which enables printers to mix the exact same colors from a set of base inks

The 8 Key elements in screen printing

1.    Artwork:
The artwork you start art with is important. If you have jagged or grainy artwork, you will reproduce have jagged or grainy artwork REMEMBER; Garbage in-garbage out. Programs for doing art in-house are available or there are art services on the internet that will supply you will screen printing artwork. If you fax them a logo, they can redraw it for you and send you a file in which you can use for the making of screens.

If you can draw the artwork yourself, it is wise to use a vector art program like SmartDesign which is a Corel Draw supplementary program. This quick and easy tool ensures that you will have high quality artwork in the end in less than half the time. Photoshop can be used as well, but this is more for full color printing, etc., which is not good to start out with since there are special techniques to master before moving into this realm.

2.    Film Positives:
When you have artwork that is ready to print, you can print your artwork out on a clear film instead of paper. For every color you have, you will print it out as a black plate on a separate film. For example, if you have a logo that is Red & Black, you would separate the two colors from themselves and print each out, changing the red to black and printing and then printing the black. Each of these would be printed on their own film by a printer, inkjets have made great strides and coupled with a RIP program have made actual cameras and darkrooms almost obsolete.

This is simply known as art separations. If the colors are touching in the final version of the logo, then you need to have what is called trap or choke. Basically, it’s an overlapping of the artwork by a small margin. This small margin is just enough so you can register the colors so there is no space between them. On the films, you will also place registration marks. These marks usually are a circle with a vertical and horizontal line passing through it. These marks will be on the same spot on each film. This will help you register your colors later it’s also a good idea to include center marks so the design will be dead center on the platen.

3. Screen Making:
When screen printing began it was called silk screening. The reason for this is, the screens used to be made from silk. Since this is no longer the case (now they are made from polyester), the name changed. A screen is simply a wooden or metal frame that has a fine mesh stretched over and attached to it. Some examples would be 83, 110, 125, 200, 230 and so on with various numbers in between. The lower the mesh count, the less detail you can print and the thicker the ink lays down. Choosing the proper mesh for the job is art form, in time you’ll learn through testing and results. It’s always a good idea to keep production records for consistency from the beginning of every job.

The actual process of screen making is quite simple, just time consuming, the most
common technique is using a light sensitive liquid emulsion although Capillary film is stilled used. Emulsion can be used under a yellow light so that you still can see what you are doing, but the UV light is filtered out so as not to effect the emulsion. A scoop coater is needed. You pour emulsion into the scoop coater and place it on a vertical screen. Pressing up against the screen and pulling up, you will lay a thin layer of emulsion on the outside of the screen. Turn the screen around and do the same for the inside of the screen. Emulsion thickness EQUALS ink thickness. For thicker stencils it’s a good idea to dry between coatings.

Once the emulsion dries, you can “expose” the screen. You need a good light source for this process. The exposure unit is basically a box with a glass top and a lid that has a compression lid or a rubber blanket and a vacuum frame. The light source would be contained in this box. To expose a screen, taking the film positive you created and place it on the glass top with the right reading being up. Then take the dried screen and place it on the glass top with the film positive under it. The screen mesh will be touching the film positive. When you close the lid, the compression lid presses the foam against the screen and the positive providing contact

At this point, the length of time will be dependent on your emulsion and light source. This is something you can talk to your supplier about. It’s really a matter of testing. Most problems occur in this stage, so it is critical that you understand this process through testing, training and trial and error. The better you are in this area, the better your prints will be. For a black light unit a 5 to 3 minute exposure time is the norm but will vary as already mentioned due to emulsion thickness and mesh count.

Once the image is exposed into your emulsion, you can take the screen to a washout booth lightly spray both sides of the screen with water. A garden hose with a sprayer on the end works well for this procedure. You do not want a lot of pressure but you do want some. After waiting for a minute, you can go back and begin spraying your screen with water. Spray on the outside of the frame, or the side that was touching the film. The inside will naturally be softer because the light had to shine through the emulsion to get to that side. A good exposure will yield less scum (softness) on the inside.

As you spray down the screen, you will see the image on your screen. What happened is, wherever there was black on your film, the light did not shine through. Since the light could not expose the emulsion, it remained water soluble. Wherever the light shine through the emulsion, it hardened and will not wash away. Lay out newsprint and pat the inside (squeegee side) with one sheet, DO NOT wipe then let the screen(s) dry. You will want to check for pinholes (little holes caused but dust, dirt) and block out with emulsion or a commercial blocking agent, then dry. After the screen has completely dried expose again (post –hardening) for a longer lasting stencil. This can be done in your exposure unit or out in the bright sun.

4.    Printing Press:
Choosing a printing press is as critical, although you are looking for a quality press. To be honest, you may want to stay away from all-in-one units and similar machines. They are a waste of money. Even though you can print just as good of a print with these machines, they are costly and they slow your process down. When your first starting, you could use a one platen machine but a 4 color-2station press is just about what you will need. Very rarely will you ever need to print anything more than a 4 color design. Later, as you grow purchase more machines that will allow for more colors. In the first years of your business, you may only have 1-6 color job. When you need to expand will suit production requirements perfectly. What you are looking for in a press is a solid frame, joystick or micro registration and rotating platens. Outside of this, startups don’t need much more than that.

5.    Conveyor dryer and flash unit:
To actually cure the ink, you need a heat source to reach 320 degrees for your ink. If you can reach 320 degrees in 1 second, it’s cured. If it’s 10 seconds, it’s cured. As long as it reaches 320 degrees, you are good. A flash unit is a unit that you place over your platen (the arm that you place the shirt on). This flash unit is meant to flash the ink just long enough where it is not cured and it is not wet. This will allow you to print colors on top of colors if needed, and you will need it! If you have a flash unit over a platen, it has to reach 320 degrees to cure the ink.

Raytek makes a heat gun that when the shirt comes out, you point the laser beam at the ink and it will give you a temperature reading, 320 is the magic number! This heat may eventually warp your platens, it will also heat your platen up enough that when you put another shirt on it and print, it might semi cure the ink in your screens, causing a clogging and poor printing so allow cool down time on long runs. The reason for this is, you would print white on a shirt, flash it, and then when the shirt comes back around to you, and it needs a second print. This gives you a good vibrant white.

If you are printing a color on a dark shirt, you would also print a white under base, flash it, then print an exact image with a different screen over top of it with the color you need. To increase your output a conveyer dryer is needed to increase your production. When you finish printing a shirt, you pull it off of your platen and place it on the conveyer dryer. Basically, it’s a dryer that has a belt on it that goes through a tunnel of heat. When it comes out the other side, it is cured. Again, use a heat gun when the shirt is about to come out, you point the laser beam at the ink and it will give you a temperature reading. Remember, 320 is the magic number!

6. Inks and miscellaneous:
The ink you will use is a Plastisol ink. There are so many manufacturers and types of inks, it’s good to find one and stick with them. Consistency is the key to success
You will also need squeegees. A squeegee is basically a handle with a rubber blade on the end. This blade is what you use to push or pull the ink through the screen and onto the shirt. There are so many miscellaneous items that it would be good to talk to Ryonet about what you need to get started

7.    Screen prep and registration:
Your scoop coater cannot reach all areas of the screen, so you want to tape out the areas that did not have emulsion, there are special tapes made to do this.
If you have a one color design, placing the screen on your press is quite simple. If you have more than one color, this is where the registration marks are needed. After placing your first screen on the press, you would do a test print. Place some ink on the screen and rest a squeegee on the frame close to the head. Pull the ink across the screen and onto the shirt then flash it. Next, take your second screen and place on the next head.
Align the registration marks on the screen to the marks on the print you made. Once in place, you can lock them in and adjust the joystick or micro registrations if necessary. Once locked in, do a test print. If everything is registered, you can tape up the registration marks on your screen and you are ready to print.

8.    Your first print:
You will be working upside down when you print t-shirts. The collar will be closest to you. After placing the shirt on the platen, pull your screen down, look between the shirt and the platen, you should have a gap. This is called your off-contact. You need about 1/8” between the screen and the platen. This will give you just enough room to make a print and allow for the screen to snap away from the shirt which gives you a clean print. Some people will push their squeegee and others will pull, whatever is comfortable to you is best for you.

Most printers pull the squeegee, which means that when you pull down the screen, grasp the squeegee and pull the ink towards you. You want to have the squeegee at an angle, if you go too much of an angle, you will get a heavy print The good thing is, if the first print does not work out for you, you can print it again, right over top of it. The registration of the machine will be the same so even if you rotated the press and came back to it, it would still print good. Rule of thumb; Angle and slow speed for light inks, less angle and a faster print for dark inks, especially printing on an under base.

Discharge Water Based Screen Printing

Discharge screen printing is becoming ever popular in todays market.  www.silkscreeningsupplies.com carries a line of discharge water based screen printing inks as well as EnviroLine water based ink that is environmentally friendly.  This blog is focused on discharge and dye discharge printing. 

Examples of Discharge Prints.

Standard Discharge	Dye Discharge: Click to Enlarge

DSPS Discharge needs to be activated by Discharge Agent which is a powder that is mixed into the discharge ink 6-10%.  You should only activate as much discharge as you will need to print at a given time as it does have a life span of about 6-8 hours once mixed.  Discharge Agent is a powder and can be ordered by the pound here.

PLEASE NOTE: YOU MUST HAVE DISCHARGE AGENT IN ORDER TO USE THE DSPS DISCHARGE SYSTEM!

To add dye into your discharge use the Ryonet EnviroLine PC 301 Pigment Inks.  PC stands for pigment concentrate and are mixed at a ratios between 5-15% (typically about 10%) into the activated discharge base. PC pigments are available in quantities of 4, 8, and 16 ounces.  

Discharge ink can be used with most 100% cotton shirts (does not work on poly or poly blend fabrics).  We recommend that you consult your shirt supplier to find out which garments SKU’s are the most discharge receptive.   Always test as results may even vary from batch to batch on the same type of garment.   

Confused about water based and discharge inks?
Here are a few helpful application charts.

Water Based Ink Type	EnviroLine WB Inks	DSPS Discharge	Discharge White	PC Pigments 301 Inks
Garment Capability	100% Cotton & Poly Blend	100% Cotton	100% Cotton	N/A
Environmental Friendly	Very	Slight Impact	Slight Impact	Mixed With: WB: YES Discharge: Some
Pantone  Matching	Yes	No	No	Yes
Required Additives	None: Ready for use.	Discharge Agent	Discharge Agent	Must be used with a base or discharge binder.
Color Additives	PC Colors for color boosts	PC Colors	N/A	Can be used with RC Inks, PC Bases, or Discharge Binders
Mixing Ratios	PC Pigments as a color boost up to 15%	Agent: 6-10% PC Ink: 5-15%	Agent: 6-10%	See Instructions
Underbase Options	RC Transparent  Opaque White Discharge   Discharge White	Used as an under base	Used as an under base	When mixing with discharge, no underbase needed.

 

Application	Type Of Water Base System	Mesh
Pantone Color Match	EnviroLine 301 RC WB Inks	156-280
Paper / Cardboard	EnviroLine 301 RC WB Inks	230-305
Towels / Canvas	EnviroLine 301 RC WB Inks	86-110
Light Garments (100% or Blend)	EnviroLine 301 RC WB Inks	156-230
Opaque Results on Dark Garments (100% or Blend)	EnviroLine 301 RC WB Inks w/ Opaque White Water Based Ink	White: 110-156 Color: 156-230
Soft Hand on Dark Garments (100% Cotton)	1. Discharge w/ RC Color Overprint 2. Discharge White w/ RC Color Overprint 3. Dye Discharge w/ PC Pigment	110-156
Vintage Look and Feel	1. RC WB Ink on Light or Dark. 2. Direct Discharge 3. Dye Discharge	Ink: 156-200 Discharge: 110-156

Ryonet Water Base Discharge does require certain safety precautions when mixing and printing.  

Read more about discharge printing and instructions for use below!

MESH:80-160

STENCIL/EMULSION: A water proof direct emulsion should be used for optimal performance. SWR-3.

SQUEEGEE: 60-80 Durometer square edge. (Ryonet recommends 60 or 70 Durometer)

MIXING:

PC Pigments: Mix 10% or less pigment with 100% discharge binder making sure to mix pigment into binder before mixing in the discharge agent.

Discharge Agent: Should be mixed 10% into 100% discharge binder (by weight).  

PRINTING: Once discharge agent is mixed into the discharge binder (with or without pigment) print directly on fabric, flash cure and print Matsui 301 Eco-Series inks directly on top (wet on wet).

Under Basing: An under base can also be accomplished by printing discharge ink, which discharges the dye from the fabric, flashing, and over printing wet on wet w/ RC Ink.  For the ultimate brilliance and soft hand results try our premixed White Discharge which has white pigment mixed in into the discharge leaving a discharged white under base.

Curing Options: Water based inks cure differently from standard plastisol inks.  While plastisol inks cure with infrared once reaching 320 degrees, water based inks cure best with air movement and heat.  Air movement is preferred to drive water out of the ink and blow away steam so heat can cure water base pigment properly. Without hot air movement across the ink, water based inks will take much longer to cure.  In good air flow, water based inks can cure in under 1 minute while it may take 2.5 to 3 minutes in a standard infrared dryer. (Paper can be allowed to air dry)

WE STRONGLY SUGGEST WASH TESTING AND DOCUMENTING CURE TIMES BEFORE BEGINNING PRODUCTION.

Level	Method	Picture	Process
Basic	Heat Gun		Heat guns actually work fairly well for curing low quantities of water base prints. Hot air from the gun forces water from the ink and curing can actually be seen as the ink dries.
Starter	Infrared Flash		IR flashes work marginally well. Take shirt off pallet, raise flash head up 4-5 inches above the shirt, cure for 2-3 minutes until ink is temped at 320 degrees. Wash test before production.
Intermediate	Infrared Conveyor		IR conveyors work decent for low quantity production. Raise conveyor gates to allow steam to exit dryer, bump temp down slightly, slow belt speed down, allow to dwell 2-3 minutes.
Professional	Forced Air Flash		Forced air is preferred for lower production or flashing. For a final cure, lift shirt from pallet to allow air to circulate under the garment.  Cure for 60-90 seconds.  Conduct Wash Tests.
Production	Air Flow Conveyor Dryer		Optimal for WB Inks, air flow gas or IR dryers can cure in 60-90 seconds depending on chamber length. Air knifes remove water from ink and IR or Gas heat cure garment.

CLEAN UP:  Card off excessive ink and dispose of in trash.  Use Sprayway Water Base Screen Opener to break down ink then wipe residue from screens, screen frames, squeegees and any surfaces in contact with ink. Left over residue can also be washed in the sink with water after soaking.

FINISHING: It is highly recommended to wash and dry garments or fabrics before packaging and shipping.

View and Download Discharge DSPS and Discharge Agent MSDS Sheets.

Water Base Discharge Inks

Discharge printing can be a valuable addition to your operation. Discharge is not a use-it-and-forget-it product. Discharge printing comes with safety precautions, issues with finished goods, and procedures for a healthy shop environment. These issues are not that difficult to deal with and cannot be ignored. Be prepared to properly handle the discharge products or don’t even try them.

Methods of using discharge

Discharge inks require an activator/catalyst to work; there are two different systems available. The predominant system relies on active ingredient Zinc-Formaldehyde-Sulfoxylate (ZFS). The newer, and less used system relies on Thiourea Dioxide as its active ingredient. There are different name determinations dependant on what the ink company calls it, in most cases formaldehyde is the active ingredient. In both systems, the ink has a limited discharge life once the activator is added. There are two methods of discharge printing, both systems can be used.

1.       The first and most traditional printing method is to discharge every color in the print; there is no need for an underbase screen. In this format you mix PC pigments into the discharge to give it color when discharging occurs.  PC pigments can be ordered in a variety of different colors and are typically mixed at about 10% into the discharge base.  This method saves a screen and does away with flashing between colors. The exception to this rule is when a black-ink screen is needed. There’s no need to use discharge if the black will cover without it. When printing on black, any black that is on the design is reversed, that part of the design will use the shirt color itself.
Example of Dye Discharge: Click to Enlarge

2.       The second method is to use discharge strictly as an underbase. With this method, you can use either white discharge or natural discharge, which contains no pigment and reveals the natural color of the fabric. The following colors are printed with regular plastisol with or without flashing.  Some prefer not to flash the discharge underbase. This saves the head used for the flash and any cool down heads. The end result is that printers can increase the amount of colors they can print on dark shirts by one or two.

The white discharge underbase works well for most design types, especially spot-color work. Even though the other colors are printed using plastisol, the overall print has a less heavy feel because the underbase is a water-based product. If a design contains halftones or other areas with very thin ink deposits, then a natural discharge would work much better. The pigment in the white discharge underbase might mix with the process inks and shift their color. This is usually a problem with spot colors.

Discharge underbasing makes true 4 color process printing on dark fabrics possible. For process printing do not use a white discharge underbase. When the white pigment mixes with the transparent process inks, they will turn pastel and muted. Work with a natural discharge underbase that will reveal the natural cotton background color using a highlight white to make the design pop. Process-ink systems can be beefed up using triple-strength versions to compensate for the natural background thus overcoming the off-white background color. Again if the design contains any white color of its own, print a white highlight that is designed to print with the process inks using this application.

Safety issues in production

Water-based ZFS-activated discharge is the most used and the most versatile method of discharge printing. ZFS has an unpleasant odor and should be handled carefully in its crystal form then blended into the ink by a properly trained employee. Always blend the ZFS slowly until it is well mixed in the ink to prevent dust, ZFS is relatively safe once in solution. Formaldehyde is a skin irritant. Proper procedure dictates dryers should be properly vented, never use an unvented dryer for discharge curing. Shirts printed with ZFS discharge have measurable levels of formaldehyde. Garments that are allowed to sit for a time after printing in an unconfined state will disperse most of the formaldehyde within days. If at all possible, avoid folding and packing ZFS-discharged garments immediately after printing.

Screen printing as a hobby or business? Questions questions questions!

A lot of people want to get into screen printing but don’t know where to start.  As we’ve already stated earlier in this blog, that’s what we’re here for.  But sometimes before you get started you should take a second and figure out exactly what it is you’re wanting to do with screen printing.  Are you all business?  Wanting to buy two automatics and a conveyor dryer right off the back?  If so what’s your business plans?  Do you already have an established line of customers you’re taping into that will be there once you get up and running?

You see, screen printing can be inexpensive to start or outrageously expensive (expensive startup can mean huge profits!) but it’s always important to have a plan.  Don’t just jump in, do some research, develop a strategy.  If you’re just in it for the hobby of it and anything you sell is just bonus that’s great.  There are many large productions shops operating today that started out with very humble goals, and even more shops that started out as a hobby and stayed a hobby.  Success is all relative and what matters is the plan you devised from the beginning and whether you are achieving what you want.  So take your time, do your research, and plan for the future.

Where to get information?

People often want to know how to screen print, how it works, and really, how to get started.  The fact of the matter is you’re just going to have to do some research on the subject.  There’s no set standard in the industry and people’s goals and what they plan to do once they begin printing all vary.  Some people want to jump straight in to an automatic while others just want to get their feet wet with a simple one color, one station press.  There are a few places to check out as far as screen printing goes though.  First off Youtube has a bunch of information on screen printing like this video right here.  But the videos on the internet aren’t usually too in depth and sometimes you need more, and for that there are a few really good sites and forums out there.  This site seems to offer a lot of free information, where as this and this forum both have a pretty hefty number of people visiting them daily.  One word on the forums though, just take everything you read with a grain of salt, most of the people answering questions on there are far from anything you would call an expert.