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 FABRIC SOFTENERS AND HOW THEY WORK

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

Dear Dr. Schiff,
Thank you for the information about soaps. Now I have another question. It is about fabric softeners. I need to know the differences between one brand and another. The salesmen talks about things like exhaustion time, slick feel and static control. Can you help me to sort through all this and find the best softener for our nursing home laundry?
Looking forward to your reply.

Ingrid S.

Dear Ingrid,

In my last letter I mentioned the importance of doing business with reputable companies. Now I would like to point out that these aren=t always the largest suppliers. In today's rapidly changing market place many of the small-to-mid-sized companies are using their ingenuity to bring innovative products to the market place faster than some of the more established soap companies. So I suggest you look at several brands.
Any reputable company will provide you with samples of their product so that you can try it under your own operating conditions, using your own water supply. You will have to be able to run this test for a number of loads since inherent formulation defects become apparent only after several softening cycles have been carried out. Upon completion of the test, ask the supplier for a written description of the most cost-effective way to use his product.

Souring and Softening

In my last letter I mentioned that the souring process will reduce the harshness of fabrics. However, this does not take the place of softening. True softening requires the use of special chemicals, which actually bind onto the fibers, imparting a pleasant suppleness.
True fabric softeners are actually surfactants. They come in 3 major varieties, with fancy chemical names: ditmacs, imidazolines and amido amines. In the wash wheel, these positively charged surfactants (commonly referred to as cationic surfactants) attach themselves to the negatively charged areas of fibers and modify the surface of the fabric and the way it feels to the touch.

Ditmac Softeners

These products soften very nicely, and impart a nice soft hand as well as a slick, almost greasy, feel to fabrics. Their disadvantage is that they are harder to wash out and tend to build up. This buildup acts as waterproofing, which is a disadvantage when it occurs on such items as towels which are designed to absorb, not repel, liquids. Ditmacs also tend to cook onto fabrics, thus dulling their colours.

Imidazoline Softeners

Softeners containing this chemical are often more expensive. However they have the added advantage of eliminating static cling better than ditmacs or amido amines.

Amido Amine Softeners

These give you the best overall balance between fabric softening and static cling control. They also have the least negative effect on absorbency. and wash out easily with no buildup.

Exhaustion or Depletion

Fabric softeners are generally acidic and also positively charged. How fast they deposit on a garment depends on the strength of the positive charge which they carry. This, in turn, depends on the pH. In very acidic solutions softeners carry a higher charge and therefore are depleted more rapidly. This is very undesirable, since it tends to leave fabrics with "hot spots" or areas, which receive too much softener while other areas, receive little or none. The ideal positive charge on a softener molecule occurs when the pH is kept between 6 and 7. At that reading, uniform softening can be obtained with ten minutes of exposure.

Static Electricity

Fabrics are poor conductors of electricity. When they tumble in a dryer, the fibers rub against each other producing static electricity. Softeners lubricate fibers during drying, which prevents this static build up. Softeners also act as conductors though which any residual static can be discharged.

In Conclusion

For the best feeling fabrics as well as for the best overall control of static cling I recommend a softener with amido amines. It should be applied at pH 6.0 to 7.0. My recommended dosage would be 0.1% active softener based on the dry weight of the load. At one-twentieth of one percent you will see a noticeable difference in the feel and cushiness, but the fabric will still have a dry feel to it. If you use one-tenth of one percent as I recommend, you will notice a very soft feel. The fabrics will move across your hand without any apparent wrinkles. Using higher amounts of softener will not give you any additional benefits and is just a waste of the product.
Because softeners have different concentrations, ask the sales representative to calculate the amount of his softener which you will need to achieve one-tenth of one percent of dry weight in the load.