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The Case for Wet Cleaning, Where Practical

Nathan Schiff, Ph.D.
Associate Editor - Institutional, FABRICARE

Have you ever played Bingo with 200 other players, while sitting in the smoking section of the hall? After the game, your clothes seem to have absorbed a lot of smoke and need to be laundered; otherwise the tell-tale stale odours will stay in the fabric indefinitely. Tiny particles of smoke are absorbed into the fibres and carry with them the composite odour of several hundred cigarettes. During a fire, a similar absorption takes place, but on a larger scale. This results in smoke and odour damage to clothing.

During combustion, several types of by-products are released into the air. These consist mainly of soot, and hot gases. Soot - which is composed of hundreds of microscopic, oily particles - results from the incomplete combustion of organic materials such as wood and plastics. New molecules are formed, some of which have a tar-like consistency and contain small amounts of aromatic compounds which release intense odours.

Because of their microscopic size, these particles tend to adhere tenaciously to the surfaces which they contact. In addition, when plastics (composed of polyvinyl chloride) burn, they also release chlorides which are mixed with the soot and smoke. When this residue comes into contact with water or any moisture, it forms weak solutions of hydrochloric acid. If the chloride level is between 30 and 200 micrograms per sq. inch the item can be restored, otherwise the damage is permanent.

The hot gases produced during combustion, also contain oxides of nitrogen, collectively referred to as NOX and which are highly reactive. The NOX, a major constituent of air pollutants, reacts readily with cotton or other natural-based fibres, resulting in permanent yellowing.

The major damage which occurs to garments after a fire is visible soot and invisible odour. The tar-like substances which result from incomplete combustion, can also act as solvents towards synthetic fibres and destroy their basic physical structure.

To prevent the spreading of soot to unaffected areas of the garments, they should first be air dried (never a commercial drier), then placed in plastic bags to be transported to a professional specializing in fire and smoke damage restoration. Drying also prevents the formation of mildew, which occurs in damp environments after a fire, and can cause staining. 

Before garments can be deodorized, the soot must be removed. The majority of items will be cotton, polyester and polyester/cotton blends. These can be most effectively laundered by using a warm water wash solution with liquid detergent, in a wet cleaning operation. Wet cleaning provides minimum agitation and therefore reduces the possibility of spreading un-emulsified soils to non stained areas. Smoke damaged fabrics may require several laundry cycles before the optimum state of whiteness or original colour can be achieved. The best detergent for use in this application is usually one which has high concentrations of emulsifiers, and a small amount of either trisodium phosphate or TKPP.

Tests have shown that emulsifying agents, rather than solvent type cleaners, provide the most efficient results. The emulsifying detergent slowly solubilizes the oil. Since surface tension is the major force which causes the soot particles to adhere to fibres, this allows ample time for the detergent to reduce the surface tension. In this manner, the non-soluble portion of the soot particles also become suspended and are thereby eliminated when the water is drained.

I realize many dry cleaners prefer to process fire orders in solvent, and this is necessary with some structured garments. But when practical, I prefer water, and the use of wet cleaning equipment.

Chemically, ozone is a highly reactive gas molecule consisting of three atoms of oxygen. Ozone has been used successfully for a number of years in a wide range of applications including food processing and preservation, beverage processing, swimming pools and spa purification and wastewater treatment. It is 13 times more soluble in water than oxygen and has an odour described as that of the smell of fresh air after a thunderstorm.

Ozone has a tremendous capacity to oxidize substances, and does so hundreds of times more rapidly than chlorine. It also disinfects three to four times more efficiently than chlorine.

Ozone s third atom of oxygen has a strong tendency to break away and attach itself to other substances, such as trace amounts of odour-causing residual soot. Just as fire oxidizes organic matter and changes one substance to another, ozone destroys the remaining odour-causing trace substances and converts them to carbon dioxide and water.

A level of ozone between 0.04 to 0.5 ppm in solution is sufficient to deodorize most organic odours. The amount used will depend on the stain and the type of fabric being deodorized. Too much ozone, just as too much chlorine, can have a deleterious effect on the garment.

1. Gently dry garments as soon as possible, to prevent mildew from forming.

2. Minimize the amount of handling to prevent soot from spreading to unaffected areas.

3. Avoid using bleach to remove stains. It may have a damaging effect on fabric colour or fibre content.


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