National Clothesline

The concept of moisture causing problems in drycleaning is confusing to most cleaners.

Many cleaners do not understand that even though your solvent is clear and not cloudy there can still be a moisture problem waiting to erupt.

In order to understand moisture you should understand the various factors that can affect the amount of moisture you can have in your solvent.

Relative humidity. This is the moisture in the air compared to what the air can hold at any given temperature. As the temperature increases the relative humidity of the air goes down because the air expands and can hold more moisture.

It is safe to conclude that on a rainy day the relative humidity of the air is 100 percent. On dry days, the relative humidity of the air is very low.

In a drycleaning plant, the relative humidity of the air is usually high because of moisture originating from the spotting gun, pressing machines and wetcleaning operations.

Solvent relative humidity. This is the moisture in the solvent compared to what the solvent can hold; ideal solvent relative humidity is 75 to 80 percent. This means that you can remove water-soluble stains and yet not affect the fabric.

Below 70 percent, the moisture has no effect on moisture and stains.

Above 80 percent, means the moisture in the solvent is capable of causing shrinkage, dye bleeding and redeposition to the fabric.

When the relative humidity is 100 percent, the solvent becomes cloudy and milky. As the temperature of the solvent increases the solvent loses its ability to hold moisture.

Fabric moisture content. This is the moisture in the fabric compared to what the fabric can hold without feeling wet. A fabric moisture content of 100 percent means the fabric will feel wet.

Fabrics can hold a great deal of moisture and still not feel wet. This is especially true of cotton, wool and silk. As the temperature increases, fabrics lose their ability to hold moisture.

Charge soap (anionic). These soaps lower the solvent relative humidity. This means the water content in the solvent is the same but the solvent relative humidity is lower, possibly to a safe level. It is not the amount of moisture in the solvent that causes a problem but the solvent relative humidity.

Batch soap (cationic). These soaps contain moisture. When the soaps enter the drycleaning machine, they are attracted to the garments and the moisture stays in the garment rather than in the solvent. Too much soap added can affect the solvent by putting too much moisture in it.

In drycleaning, everything becomes equal. There are several factors which come into play during drycleaning.

• Relative humidity of the air.

• Fabrics.

• Solvent relative humidity.

If one of the aforementioned factors contain a high degree of moisture, it will give it up to the other factors which are lower.

For example a wet fabric which is drycleaned will release moisture to the air and solvent, possibly making it into an unsafe condition. Running dry clothes will pick up moisture from solvent containing too much water.

In a drycleaning machine with too much moisture, fabrics are subject to shrinkage, dye bleeding and redeposition.

In order to do proper drycleaning, you must first determine if you have a moisture problem. There are several easy tests to determine moisture.

Run a hard, dark load. When the load comes out check the linings and pockets for breaks and wrinkles which indicate excessive moisture.

Test sample of solvent. If you put a sample of your solvent in a test tube and add potassium permanganate crystals, it will indicate moisture in the solvent if the crystals dissolve.

Check the sight glass for a milky or cloudy condition which indicates excessive moisture.

Run a hard dark load to remove any excessive moisture. Run a one percent soap charge to keep the solvent relative humidity in check.

Do not run wet garments in the drycleaning machine since they can contaminate the solvent.

Source of excessive moisture

A broken water coil.

Improper distillation resulting in a boil over.

Running wet or damp garments that are pre-spotted.

Removing excessive moisture

Run a rag load consisting of old cotton fabrics.

Use distillation but at a lower steam pressure to avoid a boil over.

Add more charge soap which will lower the solvent relative humidity.