Water-Based vs Plastisol Inks

by Gary Jurman January 29, 2015

Water-Based vs Plastisol Inks

Quick Start Information

Waterbased inks (comes standard with Merchmakr Screen Printing Kit):

Printing Info: It will eventually dry in your screen, so clean out your screen when you are done.

Drying Info: Let it air dry or force dry it with a fan or hair dryer. Then heat it to 320 F for 3 minutes to cure it. You can use an iron to dry it.

Cleaning Info: Washes up with water. If the screen stains, use Pink Power (available at http://merchmakr.com) to get the stains out.

Plastisol inks:

Printing Info: Won't dry in your screen. It's thicker than waterbased inks.

Drying Info: Do not iron. Heat to 340 F to cure it. You can use a heat gun to dry it.

Cleaning Info: Use press wash and a rag to clean up, or ink degradent such as "Sink the Ink" to make it water soluble and wash it down the drain. 

[The rest is more technical stuff]

Chances are that if you are reading this, you are learning to screen print and are curious about your ink options. Most of the time, I base my decisions concerning inks on the very first question that comes to mind for me: what kind of ink will stick to what I am printing? In the case of T-shirts or textiles, the answer leaves me with yet another set of choices: plastisol or waterbased ink. 

What is waterbased ink?

Waterbased inks are primarily water, usually around 85%. They contain binder, concentrate, other additives, and depending on the color, from less than 1% to 5% or more pigment concentrate. Some of the other types of additives are catalysts, thickeners, softeners, penetrants, anti-wicking agents, and retarders. Most commonly, these days, waterbased inks come in "Ready for Use" formulas, such as the waterbased inks that come with the Merchmakr Screen Printing System. "Ready for Use" inks are meant to be used straight out of the container.

While you can use any screen printing ink with Merchmakr, it is important to note that they are not all the same. Some inks require a level of skill and tolerance for difficulty that is much greater than others. Depending on the brand of waterbased ink you use, you might need additives, such as retarder, to keep it from drying in your screen too fast, or catalysts to make it dry faster. The inks available for Merchmakr generally don't need additives as long as you are printing 100% cotton or 50/50.

If you do decide to use additives for waterbased inks, below is a list of what the different agents do.

  • Binder: causes the ink to form a proper film, providing the correct structure for adhesion.
  • Low-Crock: helps keep the ink from rubbing off after curing (aka binder).
  • Catalyst: helps the ink cure without a commercial dryer.
  • Concentrate or Thickener: increases the viscosity of the ink, adding body.
  • Softener: makes the ink smoother to the touch.
  • Penetrant: helps get the ink down into loose fibers like in terry towels.
  • Anti-wicking: keeps the ink from bleeding beyond the print area.
  • Retarder: slows the evaporation rate for easier printing.

Generally, waterbased inks work by entering the threads of the garment and becoming part of the fibers. In order to do that, the solvent part of the ink needs to evaporate, leaving the balance of the mixture on the garment in a film state. They are recommended for cotton, cotton/polyester blends, cotton/rayon, acetate, some 100% polyester, and lycra blends. Many Waterbased inks tend to have lower opacity than plastisol inks. It is recommended that you use an underbase (print a base of white below your intended color) for printing on darker colored garments.

For a waterbased ink to dry, all of the water needs to evaporate out of it. Then you need to cure it. Merchmakr waterbased ink is formulated to cure without additives by heating it for 3 minutes at 330 F degrees.

For other brands of waterbased inks:

If you are using other waterbased ink brands, and not using a catalyst, it is recommended to use a conveyor dryer with good airflow at 330 F degrees for 3 minutes. Even with a catalyst, some manufacturers recommend heating it up to make it more wash-fast. You very much want to do a test run before printing valuable items, and wait at least 24 hours before performing it. It can sometimes take that long or longer for the chemical reactions in the ink to settle, especially in high humidity conditions. Even after waterbased ink is dry to the touch it still may need to cure.

Even after some waterbased inks are cured, you may sometimes experience crocking. Basically, if you take a dried print and rub a white cloth over the ink, if the color transfers to the cloth, it is called crocking. (Merchmakr waterbased inks should not crock.) As you might imagine, crocking can ruin your day. Basically, the reason for the effect can be due to not enough binder. As a rule of thumb, you may want about a 3:1 binder to pigment ratio.

What is plastisol ink?

Plastisol is usually composed of a PVC resin, a plasticizer, and a pigment. It is generally, ready for use straight out of the bucket, but other kinds of additives can be used for ink modification. Some additives or completed inks available are catalyst, softeners, extenders, curable reducers, and specialty agents for achieving effects like puffiness, glitters, flattening, glow-in-the-dark, photochromatic, suede, and the list goes on.

These days, not all inks that appear to be plastisol are. For the most part what makes an ink a plastisol is if the body is made of PVC. Since plastic is a petroleum product, environmentalists haven't been ecstatic about it. But the biggest issue isn't really centered around that. It's the phthalates that can be in it. Basically phthalates are a plasticizer that can give PVC its super powers. It makes PVC more flexible and durable. In recent years, many environmental regulations have come out that limit or eliminate what phthalates can be contained in plastisol inks. In order to stay way ahead of regulations and also to be as health-conscious as we can, the plastisol inks available on merchmakr.com are International Coatings inks that are non-phthalate. 

So what is the problem with phthalates, anyway? While not yet fully determined, it is possible that long-term exposure to certain phthalates could have heath risks such as obesity, insulin resistance, and other metabolic and endocrinal disruptions. Considering that before the regulations, there were phthalates in most plastics, and many pharmaceuticals, nutritional supplements, flooring, coatings, food products, textiles, and even makeup, it's a little jarring. We all have been exposed to so much of this stuff, if it is bad for you, it bears paying mind.

In most cases, you can “roll your own” plastisol in the same way you used to with waterbased inks. In color-mixing kits you can get the pigment and base separately, where the base is the ink body without any color.

Here is a list of a few of the very most common additives for plastisol, and what they do:

  • Catalyst: helps it stick to fabrics that have a very tight weave or little body to them.
  • Softeners: creates a smoother feel to the printed surface.
  • Extenders: a colorless ink base that basically stretches the pigment further.
  • Reducers: used to soften the hand (body) of the ink for easier printing or coverage.
  • Puff: makes the ink expand to have a raised effect.
  • Stretch: for printing on elastane and spandex
  • Low Cure: for lowering the temperature needed for curing
  • Foil Resist: for printing multi-color designs mixing foil and non-foil
  • Transfer: for making screen printed heat transfers

Plastisol inks are not dyes and do not actually color the fabrics they are printed on. Instead they wrap around the fibers and form a mechanical bond, gripping them. Unlike waterbased inks, what you put on the garment stays. The ink becomes solid during the curing process. It is recommended for printing most textiles that are not “woven” or waterproofed – unless you are adding a catalyst to increase it's gripping strength. Plastisol comes in some choices of opacity (ability to mask a colored fabric), and the low-bleed, high opaque versions do a good job of appearing quite bright when printed on dark garments.

Curing plastisol requires exposing the entire body of the ink to around 320F degrees. It dries to the touch at a lower temperature, so it is important to be sure that the ink is cured throughout, including the ink under the surface. Once plastisol is cured, it should be wash-fast. There are some tests you can perform to see if your plastisol is properly dried. What kind of test you perform may be influenced by your setup and needs. For instance, if you are doing professional printing with large runs, you might use a laser temperature gun to make sure the ink reaches at least the 320F degrees. In some cases you may even conduct a wash test if you are unfamiliar with the fabric type. However, if you are screen printing on the cheap in a hobby setting, you might stretch the fabric after drying the ink and check to see if the ink elongates with the pull (reasonably cured), or if it cracks or breaks apart (not cured). It is important to be sure your ink cures properly or your washability will suffer.

HINT: Did you know you can cure plastisol ink using a paint stripping heat gun found in hardware stores or at diyscreenprintingsupplies.com for around $35?

Printing Considerations

Plastisol

Plasitisol is generally ready to use right out of the bucket. Just scoop some into your screen and go. It tends to have the feel of printing with creamy peanut butter. If the ink feels a little thick or hard to pull, you can stir it first, and it should become more pliable. If it is still too hard to work, you can add curable reducer to the ink.

Temperature can also effect your inks pliability and flow through the screen. In colder environments it can be tougher to push it through the mesh. Most plastisol printers don't manipulate the printing environment at all. For instance, in Florida screen printers use plastisol in an open warehouse with fans for temperature control. Yeah... It gets hot during the summer.

Plastisol tends to be fairly opaque and the high opacity variety is well-suited for printing on dark garments. A flash dry (drying/gelling the ink layer and then applying a second pass) is used to get the brightest colors on darks. Sometimes an underprint of white ink is used to get brighter colors on darks as well.

Curing large volumes of plastisol inks can produce fumes and smoke. If you are doing big print runs you should be more concerned with ventilation. Also, some of the chemicals you use can get pretty stinky and intense. For example, spray adhesive spreads further than the area you intend; screen opener has toluene in it, and that's stinky and not real good for you; and spot cleaner is a real nose grabber as well. I know lots of guys who screen print with plastisol in their kitchen or living room, but I recommend the garage or at the very least the spare bedroom with the windows open and fans running.

Waterbased inks:

Waterbased inks can sometimes be used straight out of the container if it is Ready for Use --like Merchmakr Inks! In other cases, manufacturers recommend adding a retarder to the ink if you find it drying in the screen too fast. It tends to be pretty runny as it is around 85% water. You can thicken the ink some by adding concentrate or thickener. Different brands of RFU have different blends of the ingredients and will perform differently for you depending on the temperature, humidity, setup, your speed, air- flow, off-contact, fabric type, screen mesh count, screen weave, squeegee durometer, and what other additives you use to modify the ink. Some screen printers report that certain capillary films (ie. emulsion sheets used to create stencils) can cause excessive screen clogging as well.

HINT: Keep a spray bottle with water handy. Sometimes you can mist your ink in the screen to help keep it flowing right. With Merchmakr inks, the spray bottle is generally not needed.

For non-RFU mixtures, one ink manufacturer recommends the following blend for their ink base components:

85% Water
7% Binder
5% Retarder
3% Clear Contentrate

Then once the ink base is complete they add the pigment concentrate.
1-7% pigment (with more than 2% pigment formulas, additional binder is used)

When printing on dark garments, depending on the brand of ink, your working conditions, and your setup, you may need to underprint with a First-down white or flash dry your ink in a similar way you do with plastisol.

The environment you are printing in can greatly affect how your waterbased ink performs. Temperature and humidity can be major factors in how well your printing session goes. I have heard of people trying to print in low air-flow situations and running humidifyers to help aid the process. One of the biggest problems I have had while constructing this document is that there is a pretty wide variance in formulations for the waterbased inks, and because of that, information can sometimes be conflicting. Throw in with that, some waterbased inks also contain discharge agents (they displace the dye in the fabric) which completely changes a huge number of factors. Because of all the variance with waterbased inks, you would do well to consult the manufacturer's specs (aka. MSDS) as far as what your health, safety, and ventilation needs might be.

Printing Techniques

Plastisol

When printing plastisol inks, a medium durometer (70) and a 156 mesh screen is a good general purpose way to start. For low detail, thick, or light colored inks it works well to use a 110 mesh screen instead. If you are doing thinner lines or small dots in your art, a 200 mesh screen is a good way to go. I wouldn't mess too much with different durometer squeegees to start with, but I will say that a cut-edged squeegee (sharper) is better for capturing higher detail, and a molded edge squeegee is better for light colored inks and low detail. There are a variety of squeegee pulling or pushing techniques you can use according to your needs, and how much off-contact you use is also a variable. The idea is to partially penetrate your fabric deep enough for the plastisol ink to get a grip on the fibers. Then you want to leave a thin layer of ink on top of the fabric for a nice finish. Experienced printers may be able to do it in one pass, especially with dark colored inks. You may need several passes with the squeegee to get your coverage right.

Waterbased

Waterbased inks do not need to penetrate the fabric to be wash-fast. The binder in the ink forms a chemical bond with the threads, and that's where the color adhesion comes from. Once the water is evaporated out and the ink has cured, the binder forms a film that holds the pigment inside. Too much penetration in the fabric leads to longer cure times and also to waste.

When printing with waterbased inks, a good benchmark mesh would be a 156, avoiding silk and nylon make-ups as they may react with your ink. You can use a medium durometer squeegee, and a molded or cut edge work fine. A good practice for screen making would be to re-expose your screen (called post exposing) a second time after the stencil has been washed out. That will make the emulsion more water-resistant and your stencil will last longer. You'll want to be sure that you use an emulsion that is suitable for waterbased ink printing, as well.

The following is not needed with Merchmakr inks:

One printing technique that may help you immensely when printing waterbased or any air-dry ink that threatens to clog your screen is to use a flood technique. When trying to keep your screen from drying, you'll want to keep wet ink in the image area of the mesh as much as possible. That means that between doing prints you need to keep a layer of ink wetting your screen.

Here's how you do a flood: Your print cycle should be as follows:

  1. Print: Lower your screen onto the fabric and pull your squeegee, executing the actual print.

  2. Flood: Lift your screen off the printed fabric (because your print is complete), then (with the screen still off the fabric) lightly push the ink back over the image again, leaving a thick layer of wet ink on the mesh. Set the screen in the resting position (up and waiting for the next print) so that you can move on to the next step.

  3. Material Handling: Unload your platen with the printed fabric. Reload the platen with the next item to be printed.

Now you're ready for the next print.

Cleaning Up

Plastisol Inks

Plastisol inks can be cleaned up several ways. The most eco-friendly way is to use citrus- based products. We recommend an ink degradent (such as Sink the Ink) that you spray on the screen and scrub with a pad. It makes the ink water soluble and safe to run down the drain. In addition, you can use a press wash and a rag. You can use mineral spirits to clean the ink as well. It is not a “green” solution and needs to be handled and disposed of properly. Lastly, you can use screen opener. I do not recommend that at all because it is very noxious and quite bad for you. The only thing I use screen opener for is unclogging tiny areas of a screen during a print run, and I use it very sparingly.

Waterbased Inks

Waterbased inks clean up with water. Merchmakr waterbased inks can be run down the drain. If the ink stains the screen too heavilly, use Pink Power (haze remover) to remove most stains.

Waterbased and Plastisol Pros and Cons

Waterbased Inks Pros

  • it has a softer hand to it and doesn't have the bullet-proof feel of some plastisol prints
  • in some cases of high volume printing it may be less expensive than plastisol.
  • It is easier to clean up
  • It needs less equipment to cure

Waterbased Inks Cons

  • You need a hardier emulsion (for larger runs like several hundred units) to keep it from breaking down. Unfortunately, that makes it harder to reclaim(recycle) your screens.
  • Screens need to be cleaned immediately after a print run or they'll be ruined.
  • Your environment (such as humidity) can impact your print run.

Plastisol Ink Pros

  • screen making can be less complicated (for larger print runs).
  • screen reclaiming is easier (for larger print runs).
  • doesn't dry in the screen. You can leave screens with ink on then up on the press for months with no problem.
  • quicker drying, which means your dryer needs fewer features.
  • better stretch with fabrics.
  • many more additives for effects.

Plastisol Ink Cons

  • has a textured feel to the print and can be “thick.”
  • Plastisol is a petroleum product and is subject to associated objections.
  • Older plastisol inks may contain phthalates. No plastisol inks sold by Merchmakr.com contain phthalates.
Gary Jurman
Gary Jurman


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