Frequently Asked Questions (FAQ's)
"What IS Tack Cloth ?" Tack Rag ( ták klôth ) ─ a specialized type of wiping cloth that is treated with a tacky material, and designed to remove loose particles of dust, dirt and lint that would otherwise contaminate a surface that is to be painted, coated, laminated, photoetched, or otherwise prepared for some finishing process ( more ─ see Glossary ).
"Why use Tack Cloth ?" Tack Cloth will remove dust, dirt, fiber and other (solid, dry) particulates from a prepared surface -- and also remove them from the surrounding environment -- that are not completely removed by brushing/sweeping, vacuuming, wet wiping and other methods. You can easily demonstrate this performance in your own application by tack-wiping your critical surfaces after your other cleaning methods have completed, and then see the residual contaminants on the Tack Cloth that your other methods failed to remove.
"What are Tack Cloths made from ?" Traditionally, Tack Cloths have been made from cotton cheesecloth (medical gauze) which is favored for its cleanliness, absorbency, suppleness, and open weave (to entrap particles). Some Tack Cloths are now made from synthetic monofilament yarns to eliminate the spun fibers of natural fabrics, like gauze, as a source of contaminating lint. Other Tack Cloths are being manufactured from low-cost nonwoven fabrics.
Tack treatments, as with adhesives and much like paints, can be made from solvent-borne, water-borne or hot melt systems. Solvent tackifier systems have now been largely abandoned in the US due to health and environmental concerns with the VOC (volatile organic content), the drying-out of tack as volatiles evaporate, the trace residue left by out-gassing of volatiles, and the overall superior performance of other systems. Water-borne tackifiers are found most commonly in non-woven Tack Cloths, and may offer some performance advantages in certain applications. But it is the hot-melt systems which now dominate the industry and that are generally favored for their lack of volatiles (organic solvent or water), long shelf-life and stability, and relative friendliness to health and environment. Contrary to folk lore, modern commercial Tack Cloths are not made with "varnish", "lacquer" or "beeswax".
The designs of many brands, particularly those favored by major markets like automotive assembly painting, are closely held trade secrets. While specific materials wont be cited here, it may be helpful for some professionals to consider tackifier treatments in the same way as paint formulary: in a multi-component tackifier, a base resin may serve as a "binder" for added tackifiers and other "solids", and may also include "fillers", "plasticizers", performance "additives" like antistats, and even pigments or dyes. In a hot-melt or "thermoplastic" tackifier system, heat serves as the "carrier" instead of volatile solvent or water. Water-borne tackifiers are favored in some applications and may see future development.
It is important to understand that the greatest cost factor in Tack Cloth is in the quality of raw fabric ( e.g., basis weight, size, composition and construction). That is, cheaper Tack Cloths are made with cheaper fabrics: lighter basis weights, looser weaves, uncombed fibers, short-cut sizes, nonnwoven fabrics, etc. In general, heavier fabrics and tighter weaves make for better Tack Cloths, and the costs are commensurate with these qualities. Because fabric qualities are often overlooked by the uninformed buyer, it has become the increasingly common practice among many Tack Cloth vendors to deliberately short the fabric features (especially gauze thread counts) and sizes (esp. cut length) below the advertised specifications. So it is critical to compare the physical ─ and not just the advertised ─ fabric features when comparing the prices of Tack Cloths. For example, the USP ( United States Pharmacopoeia) specifications for the construction of medical gauze should be the guide for comparison of Tack Cloths made from cotton cheesecloth.
Less of a contributor to cost, but equally important to performance, is the design of tackifier treatment (and by extension, the treatment process). Some of the important characteristics include viscosity, melt-point, wet-tack (quick-stick), adhesion and cohesion ( more ─ see Glossary). In general, low-viscosity (more liquid-like) tackifier treatments are the easiest to use in Tack Cloth manufacturing -- often alone and without performance additives -- and are thus commonly found in bargain brands. But the wetter or oilier texture of these materials requires that the cloth hold less of the tackifier so that the incidence of resin transfer is minimized. Thus, these simplest of Tack Cloths are less effective in picking-up and holding large amounts of dirt while they pose and increased risk of residual contamination.
Conversely, higher-viscosity (solid and semi-solid) materials are much more stable in tack-off applications. So these materials can be "loaded" into the cloths at higher treatment weights, and can also serve as binders for a variety of other performance additives to allow for much broader capabilities in tackifier formulary. That translates into greater ability to absorb dirt particles and to resist resin transfer. In addition, the higher-viscosity materials allow for a greater range of formulation for performance: wet-tack (quick-stick), adhesion, cohesion and other characteristics ( e.g., "slip versus grip") can be optimized for different tack-off applications. However, the higher-solids, higher-viscosity materials are more difficult to use in the manufacture of Tack Cloths and thus require more highly sophisticated processing technologies.
"What causes tack transfer?" When a good quality of Tack Cloth is used properly, the tackifier treatment should not leave any trace residue that might interfere with a finishing process. However, an unsatisfactory experience due to tack transfer is often a reason why some finishers refuse to use Tack Cloths. The problem can be easily avoided, and the desired results obtained, if some simple abuses can be avoided.
Quality and Design of Tack Cloth -- Low-viscosity tackifier treatments, even if they are only a light weight (or "loading") of the treatment material, are not as readily bound to the cloth ( i.e., are poorly "cohesive"), and are therefore more easily transferred (as well as holding less dirt). Those made with an organic solvent (VOC), while increasingly rare, can leave residues from out-gassing of volatile components (even evaporation of residual water, from water-borne tackifiers, can deposit contaminants). Low-viscosity and solvent-based treatments are typical of bargain brands as they are easier to manufacture.
Excessive Wiping Pressure -- One of the most common causes of tack transfer, users may be inclined to rub with a Tack Cloth, either as habit or from using a poor quality design.
...to be continued
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