How to Coat a Screen with Emulsion

Posted by Mary Yaeger - 9/18/2017

Also seen on Printwear 

Coating a screen is also referred to as “making a stencil”. The process is done with emulsion which is a thick liquid that is sensitive to UV light. When you place artwork on the photo sensitive emulsion and expose it, a negative stencil is created. This negative stencil is what allows the ink to be printed on a garment.

Before we get into coating a screen we need to discuss the different types of emulsions that are available. There are three types of emulsion and capillary film – which could be used as an alternative to coating the screen. All emulsions work with plastisol inks. Water based inks will eat through most emulsions so you will use an emulsion formulated to work best for water based printing.

Diazo Emulsion

Diazo emulsions have been used for many decades and are still preferred when low production cost is a major consideration. Diazo emulsions are either water resistant or resistant to UV and solvent-based inks. Plastisol inks may be used with either diazo emulsion type.

Dual Cure Emulsion

Diazo-Photopolymer emulsions, also known as dual-cure emulsions, offer the largest variety of features and applications. Dual cure photo-stencil systems provide remarkable image quality and exceptionally durable stencils. These are premium emulsions for use with UV, plastisol, water-based, and solvent-based inks. Whether you need an emulsion with high chemical resistance or one specifically for ceramic inks, our selection provides the right emulsion for your requirements.

Pure Photopolymer Emulsion

Photopolymer emulsions are one-component emulsion systems that are pre-sensitized and ready for use. They offer very fast exposure speed and can be used universally, but often are developed for specific applications and exposure equipment such as direct projection, high emulsion over mesh ratio or for coarse mesh counts. Photopolymer emulsions are typically resistant to UV, solvent-based and Plastisol inks.

Capillary Film

Capillary film can replace liquid emulsion as the technology necessary to meet a wide range of decorator demands, including textured garments, textured prints, and higher resolution images at a lower production cost. Capillary film is not messy like liquid emulsion, does not require mixing ingredients, does not require storage in the refrigerator, and has a longer shelf life. There is no waste, since you cut off and use just what you want.

Application

Emulsionscoop coaters are a must-have tool for coating screens with all direct liquid emulsions. Emulsion scoop coaters are the perfect way to get a smooth, even emulsion layer on your screen.  Simply pour an appropriate amount of emulsion into the coater reservoir then position the coater against the screen and move slowly and smoothly from the bottom to the top, adjusting the angle of the coater slightly as you go to ensure good coverage.  

It is usually best to get an emulsion scoop coater about 2-3 inches narrower than the inside screen frame width. You want the coater to be just wide enough to cover the entire emulsion width in one pass. For heavier ink deposits or to increase the durability of the screen for longer runs additional coatings may desired after the 1st application dries. This will provide a thicker more durable stencil. 

Now, you are going to start with a screen that has been degreased and dried without being contaminated with dust, lint or finger prints. Next, you are going to fill the scoop coater with emulsion. Place the screen frame in an upright position and secure it in place. Use two hands to hold the scoop coater.

When coating screens the emulsion needs to be even on the mesh. Thick and thin places will cause problems during drying and exposing. The thin places will expose faster and cause the image to not wash out due to over exposure. The thick places will expose slower and cause the image to break down and wash out.

There are three types of coating methods:

1&1 Coat – Apply one coat of emulsion on the print side, rotate the screen 180, and apply on the squeegee side. Dry in a horizontal position.

2&2 Coat – Coat twice on the print side, then twice on the squeegee side. After each coat, rotate the screen 180. Dry the screen print side down. This will require a longer dry time, longer exposure time and yield a thicker stencil. This coating method is great for athletic printing.

3&3 Coat – Start by using method 2 above. After complete drying of the emulsion in method 2, add an additional coat on the print side and dry again. This method produces the sharpest edges and thickest stencil and ink deposit.

After coating the screens, let them sit overnight to dry. Screens need to be dry to the touch before exposing.

Underbase Printing

Posted by Dustin Koch on 9/12/2017

What is Underbase Printing? 

This is a bottom layer of ink used to optimize the brilliance and quality of a print. The most common under base used is the main white ink that a shop is using, and it is most commonly used on darker garments in order to deliver the quality of colors the job needs. There are other ways to print an under base, but this lesson will be focusing on using white ink to achieve a quality print. 

Why use an underbase? 

Well, have you ever tried printing a red ink on a black shirt and wonder why it appeared to be "off looking" or "flat?" Most printers have gone through this as well. Under basing takes that "flat" look and turns into a "popping" look. This process enables you to give a better looking product to your customers that will have them coming back to you for future orders. Yes, an under base on a shirt will cause a thicker print on a garment, but the trade off is a much better print and much better satisfaction in your customers.  

What Inks Should I Use?

When using a white as an under base, choose a white that is smooth, soft, and high in opacity. This will allow for the best result while the other inks are being printing on top. As far as the other colors, using a medium opacity ink like the Texsource GEN Series would be ideal. Texsource Prime Time, Texsource White Dream, and Texsource Odyssey White are great for cotton and cotton/poly blend garments. Rutland Super Poly White and Triangle 1706 are great for Polyester garments.

Tips for Underbase Printing Printing:

Printing

A great under base will result in a great finished product, whereas, a bad under base will result in a bad finished product. The first layer of ink laid down will need to be smooth and consistent in order to be successful. This may require a double stroke on the white or a print, flash, print before moving onto the other colors. Each garment reacts different to a stroke of white causing for the printer to need to know his/her inks and his/her garments for the best results. 

Trap It! Choke It! 

It is very often that customers have issues registrating an image that requires an under base. The best way to resolve this issue is not necessarily on the press, but rather, in the artwork. There are two different methods that can be used to help registrate an image properly. Option one is to choke the under base by 1 point. Choking the under base simply causes it to be slightly smaller than the inks that print on top. This will allow for the white ink to "disappear" when the print is complete. The second option is to trap the ink on top by 1 point. This process causes the image on top to be slightly bigger than the under base causing it also to "disappear." 

Mesh Count 

The most common mesh counts for the under base white are a 110 and a 160. This allows for a solid and smooth image area for the other inks to print on. Higher mesh counts can result in a less desired look to the finished product because it will not allow a good base for the primary colors. Because printing on top of an under base is like printing on plastic, a higher mesh count will be needed for the colors going on top. Anywhere from a 200 to a 305 depending on the detail needed

Tools of the Trade - Screen Openers

Posted by Mary Yaeger – 9/6/2017

Why have screen openers in your shop? Simple. Sometimes ink will “dry up” an area of your screen which has the possibility of ruining the image area and the mesh itself. Not only does this slow down your production time, but it could cost you money in the long run. Regular use of screen openers helps prevent clogging and work delays.

Screen openers are used by screen printers everywhere. Just as there are many different screen printers, there are many different brands of screen openers. This fact alone can make it difficult to determine where to start when you buy one, but it is important to note they all have their advantages depending on the type of printing your shop does. Screen openers typically come in two forms – spray and foam spray. Both forms of sprays are meant to be used with different types of inks – water based or plastisol.

As mentioned in previous articles, plastisol ink does not “dry”. It has to go through a curing process to be considered “dry”. So, when we say an area in the screen has dried up, what does that mean in terms of plastisol ink? Depending on the mesh that you are using (especially really fine mesh), plastisol essentially gets lodged in between the mesh threads. When this happens, your standard press wipes or press wash won’t penetrate those threads well enough to get the plastisol out. This is where screen openers come into play. Screen openers are a more aggressive version of press wipes/wash. And can get in between the fine threads to remove the ink.

Water based inks are a little bit different than plastisol in this case. With this particular type of screen printing you will run into ink drying, but there are screen openers made specifically for water based inks! Most screen openers recommend regular use of screen openers. Not only does this open dried up areas on the screen, but it prevents clogging in the first place. It is important that when you use water based inks you keep the screen wet to prevent the ink from drying. Water based screen openers are another tool for screen printers to ensure they are protecting their mesh and keeping up with quality and production.

Another great aspect about screen openers is that they can also be used to clean ink and dirt from your press. While press maintenance may not be high up on a shop’s list of to-do’s it is important to remember to occasionally wipe your press down to protect it.

How to use a screen opener:

When using a screen opener it is important to remember that you are using a chemical. There are some screen openers that smell bad and there are some that smell fruity (typically oranges). That being said, remember to open a window or turn on fans as to inhale as little chemical as possible. Whenever you run into a screen clogging issue, spray the screen opener in a circular motion 6 to 8 inches away from the screen to open. Only a thin application on dried-in areas, and a few passes with a clean rag, is needed to open the mesh back up! 

Typically screen openers do not leave an oily residue or film, but it is important to check with your supplier to make sure you are getting the right product for your shop.

To learn more, visit us online at screenprintingsupply.com

How do I choose the Right Exposure Unit?

Posted by Mary Yaeger - 9/5/2017

Currently in the screen printing industry, there are 3 main types of exposure units - UV, LED, and Halide lamp exposure units. Figuring out which one would be the best fit for your shop can be a confusing experience so we have listed some of the key differences.  

The most economical choice is a UV exposure unit, often available in a tabletop model or with a stand.  They are reliable and easy to use and maintain. They offer great performance and versatility at the best price.  This is an excellent choice for a startup shop or those looking for value. 

LED exposure units are relatively new to the industry.  They offer greater energy efficiency, lighter weight, longer bulb life, and can significantly decrease exposure times when used with the proper emulsions.  This type of exposure unit is recommended for higher production shops or those who desire better performance than UV units. 

 

Lastly, Halide lamp exposure units are the workhorse of the most demanding shop environments.  They offer larger size exposure areas and the highest resolution exposures available.  They have a short 'warm-up' time and they can offer extremely fast exposure times once in use.  

To learn more about these products, visit us online at screenprintingsupply.com