Spot Cleaning 101

Most T-shirts and other imprinted garments contain a blend of heart, soul, creative genius and sweat. You have created, nurtured and massaged it (well, squeegeed it). It is yours, your baby, nothing will ever harm or hurt it.

At first you pretend not to notice. There’s nothing there. There can’t be. It couldn’t be. Say it isn’t so. Then reality (and depression) hits; there is an ink smudge on your baby. Your immediate response is of course thoughts of suicide, or even worse throwing it in the garbage, which is no way to treat your baby.

By now any seasoned screen printer who has been around the block, or in fact one who has just turned down the first street, knows about spot cleaning guns. Sometimes called “blow-out”, “knock-out” or simply “spotting guns”, these compact units are the surgeon's scalpel to screen printers, able to instantly cut away unwanted ink and soils from the fabric. Just like surgeons though, spot cleaning guns do have their limitations. Some times it simply isn’t practical to remove a large design or ink mark, as it would take more cleaning fluid and time than the garment is worth.

Spot cleaning is accomplished by shooting a high-pressure jet of a specialized cleaning fluid through the offending soil. The chemical is forced into the ink, breaking it down and then by the sheer pressure of the fluid stream, it is blown out of the back of the fabric. Because of the way in which these guns work, they are only effective on porous fabrics that have been woven or knitted. Vinyl, plastic or any type of leather or animal skin cannot be cleaned in this way.

At first look, there appear to be as many different manufacturers and brands of spot cleaning solvents as there are press manufacturers (no offense guys). At second look there are still just as many, however, let me offer the following to try and simplify the decision. Spot cleaning fluids can be separated into three basic types. Firstly there are the non-flammable products based upon Methylene Chloride, d.b.a. Dichloromethane, d.b.a. MEC. These are by far the widest used cleaners out there and for a very good reason; they simply are the most effective ink removers. The Second group is flammable solutions. These normally contain a very high content of Acetone (some times they are 100% Acetone). The obvious draw back here is the flammability issue. As a cleaner acetone, does OK, however, you can expect a higher degree of color bleed (ink running into other parts of the garment). The final types are also the newest kids on the block; they utilize a solvent called 141B Dichlorofluoroethane. This product was developed as a replacement for some of the previously phased out Freon products. As a cleaner it will remove plastisol screen printing inks, it does however, take more product to accomplish the operation. Another big draw back with these types of product is their costs, typically about 50% higher than conventional spot cleaning fluids.

 
 
Methylene Chloride Based
Acetone Based
141 B Dichlorofluoroethane  Based
Plastisol Ink Removal
Excellent
Good
Good
Water Based Ink Removal
Good
Good
Good
Color Bleed
Minimal
High
Medium
Flammable
Typically No
Yes
Yes*
Specialized storage Required
No
Yes
Sometimes
EPA Regulated
No
No
Yes**
OSHA Regulated
Yes
Yes
Yes
Single Gallon Cost
$15-22
$9-14
$22-28

* This product is in it’s self non-flammable, however, the other solvents used in the blends are normally flammable.
** Products containing 141b Dichlorofluoromethane are required to carry a ozone depletion warning on the container

The second half of this spot cleaning partnership is the gun. Just as important as the chemical used, the gun must be suitable for the job at hand. If you are a smaller shop, you may not need all of the bells and whistles that the high end guns offer. At the other end of the scale, a large shop with a high production rate will probably want the most cost-effective, efficient means available for spot cleaning.

To better understand which type of gun is right for you, it is important to know how these pint-sized dry cleaners work. In their simplest form they are nothing more than airless paint spray guns, similar to those available at home centers. The fundamental differences are as follows.

  • The materials that they are made from, as they must resist very aggressive solvents.
  • The specialized nozzle (nozzle uses are covered later in this article)
  • Their weight. Spot cleaning guns must be light as the solvents used are typically very heavy; this combined with a heavy gun would cause the operator to tire very quickly.

Airless means exactly what the name implies, they do not use air as their source for power, instead electricity is used. They use an electro-magnetic motor that cycles with the electric current at 60 times a second (60Hz). A steel plate, which is connected to a piston pump, is pulled back and forth by the magnet. These pumps have the potential to produce pressures approaching 2000psi. It is for this reason that extreme care must be taken to not place fingers, limbs or other appendages in front of the gun when in use. This also includes pointing it at other people.

Guns range in price from as low as $100.00 up to $450.00. At the low end you may get a basic gun with a fixed straight stream nozzle. Normally this can be upgraded to an adjustable nozzle for a few dollars more. The smaller guns normally produce a pressure of about 1000psi. This is adequate for ink removal, it is obvious however, that if it is pressure that blasts the ink out, then more pressure will do the job more effectively. Higher end guns offer standard features such as fully adjustable nozzles (mist through jet); larger reservoirs for chemical and higher pressure (up to 1750psi). Other optional accessories that can be fitted to these higher end guns include Air Dryers and Direct Feed attachments. Air dryers are special nozzles that once fitted to the gun, utilize a compressor to provide a blast of air to help dry the fabric. The direct feed attachment is a replacement for the reservoir on the gun. It draws the spot cleaning fluid directly from the jug or barrel, allowing continuous operation, without the need to refill the gun.

Choosing a gun is very much like buying a car. You buy what you need. If you are a family of two, then you would probably only need a compact or mid size. A larger family would probably opt for a mini van. Which gun is right for you? If you have a small shop and limited production then a smaller less expensive unit is fine. I do however, highly recommend adjustable nozzles. They make the gun far more versatile as a cleaning tool. High production shops should look for high pressure, available accessories and reliability. Reliability can often be measured by how well a manufacturer backs up the product. The warranty should say it all. A long warranty implies quality and reliability. Not many people would lay down their hard-earned dollars for a new car if it only came with a 6-month warranty. The same should be a benchmark when shopping for spot guns.

In today’s environment of work place safety, vacuum exhauster units are becoming more than a luxury, they are now a virtual necessity. New laws have now lowered the acceptable exposure levels of many spot cleaning chemical. Most exhausters have been designed to allow compliance with the new standards of workplace safety. Exhausters have two main functions. They, as the name implies, exhaust the contaminated air away from the operator, while they simultaneously dry the fabric being cleaned. These units are NOT air cleaners,the exhaust hoses still need to be vented outside or into an open area. The hose should always be installed as low as possible, as most spot cleaning fluid vapor is heavier than air, and has the potential to fall back across the breathing zones of operators, if vented too high The second big advantage is high speed drying. This controls ringing and color bleed. By minimizing the amount of chemical spreading out on a shirt, you greatly reduce the likelihood of bleeding ink and causing a stain or ring (a ring is a concentration of ink, dirt particles or fabric finishing chemicals, that build up at the edge of the wet area).

When shopping for an exhauster, the same basic rules apply as for buying spot guns. The warranty should be your first clue, if it’s backed well, then it’s probably built well. Because of the job that it has to do, high airflow is paramount. Airflow is measured in CFM (Cubic Feet of air per Minute); a flow of 500 CFM is an acceptable level for most shops. The cleaning screen should be stainless steel, and sized so that you can lay the soiled area and surrounding fabric over the vacuum unit. If it is too small an area, the fluid will run out in the fabric and take longer to dry, possibly causing ringing or stains. If the cleaning surface is too large an area, then the fabric will take longer to dry, as the air will be diverted to other parts of the cleaning screen. Tabletop exhausters now offer very high performance without the high price tag. They can be placed on a bench or table and do not require additional floor space. An additional consideration when shopping for an exhauster, is it’s compatibility with flammable cleaning fluids. If your solvent is flammable then you must use an explosion proof unit.

As a final note on exhausters, before all you inventors rush out and grab your Shop Vac, PVC pipe and toolbox, consider the following. Shop Vac’s have a tank that will allow the spent solvent to accumulate. This in fact becomes hazardous waste that you will need to dispose of. Exhaust units completely evaporate the chemical, so that there is nothing to dispose of. Additionally, the life expectancy of a Shop Vac when used with spot cleaning solvents is about 3 months; you do the $ math!!

Tricks of the Trade

OK so you’ve researched, shopped and then laid down your hard-earned dollars for the best spot cleaning system your money can buy. Now what! Spot cleaning guns are as important as your printing press. You own the press for one reason, to make you money. If you get a mark down or a spoiled shirt you are loosing money. The gun recovers that lost profit. The first step is to determine if the time and material cost to salvage a print is cost effective. If you are intending to remove a complete back design from a $3:00 T-shirt, it probably isn’t, however, if it’s a $35.00 jacket, it becomes far more viable.

When spot cleaning plastisols, always make sure that the ink is completely dry and cured, otherwise it will run and give you a bigger mess to clean up. Other inks such as water based and catalyst inks, should be tested prior to printing. First try it cured; if the results are unsatisfactory then try it uncured. For small spots, smudges or fingerprints, place the shirt over the exhauster (or a dry scrap shirt). Using a pin point jet, holding the gun about 6” from the fabric, start circling around the soil, spiraling into the center until the ink has been completely removed. Care should be taken not to allow the jet to hit any part of the image, as this will damage it and “really” destroy the shirt. To avoid the formation of a ring, especially on darker shirts, the following feathering technique can be applied. Immediately after spotting, adjust the nozzle to the widest fan setting. Spray around the edge of the damp area in a continuous manor, spiraling out and away from the fabric. The results should leave a smooth transition from wet to dry, with no sharp edges, and when dry, no ring

For marks that are very close to the image a slightly different approach is needed. This is where a steady hand is needed, so early to bed the night before. Adjust the nozzle so that it produce a spray pattern of about ½” from a distance of about 6”. Start spraying on the side of the mark furthest away from the image; slowly move through the soil until it is flushed away. This will take slightly longer than usual, as less pressure is being used. An advantage of this technique is that the softer spray has less potential to damage the image, should it momentarily contact it. This same technique can be used to eliminate ghosting or double imaging, caused when a screen misaligns over a shirt and transfers some built up ink. Simply run it along the edge with a medium spray until the shadow has gone.

Never! Never! Never! run the shirt back through the dryer to dry it. This, besides the obvious risk of a flash fire if a flammable solvent is being used, will guarantee one thing... a ring! To dry the shirt, use an exhauster, air dryer or a combination of both. The faster you dry the shirt, the cleaner your cleaning will be. If you do not have either drying device, you can use a clean airline or even the cool setting on a hair dryer. If all else fails then wave it in the air, this will dry the shirt and also let your customers know that you surrender.

Spot cleaning guns are not miracle makers. They are not a replacement for good housekeeping in the print shop, nor will they keep the printers hands clean. They are however, a first line defense against markdowns due to soiling. Like anything else they are tools that need to be used correctly and safely. By following the above guidelines, spot cleaning can be accomplished very effectively and cost efficiently. Remember to keep in mind that it was ruined before you started, so you really can’t make things any worse.

Happy spotting. Now if I could just get this damn coffee stain out of my shirt.