Original and vintage quilts and textiles
  The skinny on Orvus Paste.

Orvus Paste is widely marketed to quilters as a sort of Miracle Cleaner. Some people insist that quilts and vintage textiles must not be washed with detergent because detegent is "harsh," and that the reason Orvus is recommended is because it's a "soap" and "gentle".   Others go so far as to claim that a quilter will "ruin" her quilts if she uses anything but the magical Orvus. What a guilt trip.

Truth is, Orvus is detergent. It was designed to be body wash for cows and horses.  Its value lies not in some secret, special ingredient, but in what's not in it - softeners, fragrances, bleaches and brighteners which may adversely affect fibers over time.  (Fabric softener, for example, leavs a film that can attract dirt, and dirt is one of fabric's biggest enemies.)

The other truth is that the price of Orvus in quilt shops (averaging 75 cents/ounce) is six times higher than if you ordered it online from a livestock supplies shop.  Just use your favorite search engine to search on "Orvus" and "horse" to find lots of suppliers.

So what gives?  Is Orvus really worthy of its cult status?  If you decide to use it, what should you know?  

Kay Lancaster recently responded to this question in a recent issue of Creative Machine's online newsletter.   I reproduce it here, with many thanks to its knowledgeable author.

...Orvus,a/k/a sodium lauryl sulfate or SLS (same as sodium dodecyl sulfate) is an anionic detergent, not a soap. (If it were a soap, it would be a pain in the posterior to use in hard water areas, forming grey, insoluble scum.)  Conservators use Orvus because it doesn't have the optical whiteners and brighteners and bleaches, etc., and rinses out fairly well most of the time, except in very hard water-- you need many, many more rinses in hard water areas. (Conservators typically use water purified by reverse osmosis or by deionization to get around the hardness problem.)

Because it lacks optical brighteners, bleaches, builders, etc., it's not going to foam the  way you think of most detergents foaming, and it's not going to give that "whiter than white" look you get from commercial laundry detergents, and things may start looking dingy after repeated use.  (Optical brighteners are compounds that absorb ultraviolet light and re-emit it in the blue wavelengths.  Absorbing UV and re-emitting the energy may be good for long term light stability).

Orvus also lacks "antiredeposition agents", which means compounds that keep the dirt that's now suspended in the wash water from re-depositing in the fabric.  You get around this with Orvus with multiple rinses... textile conservators may use 20 or more rinses.

Best pH for getting greasy dirt out of clothes is quite alkaline, about 10 or so, so you may have a tougher time getting greasy dirt out with straight SLS, which generally has a near-neutral pH.

There are some other potential gotchas to using it under some conditions: adding vinegar or other acid to rinse water (which you'd typically do with a soap, and might do with wool or silk) can force the water's pH down to the point where the SLS chemically bonds to the wool or silk fibers.  If you treat fabric like a textile conservator, you can then rinse in deionized water till the cows come home and rain falls up, and you're not going to get it out of the fabric again.

Fabric softeners (and some of the germicides like quaternary ammonium compounds) are cationic detergents; they will react with anionic detergents like SLS in a reaction called "reverse saponification," which leaves a greasy, waxy goo on the fibers that's difficult to remove without using high pH (very alkaline) conditions or solvents.  If you leave it in the fiber, the goo will attract more dirt quickly.

Finally, there are some skin safety issues. Wear gloves or use a spoon or point of a knife to handle Orvus paste, and make sure the solution is pretty well diluted before you put your bare skin in contact with it. It's a pretty good irritant to skin, and can cause allergic reactions, dermatitis and eczema for some of us lucky souls. It can also sting pretty badly, especially if your skin is damaged in any way to begin with. We used it in biology labs for (among other things) breaking cell membranes so we can get at the contents of the cells -- it can do the same thing to skin cells.

And if you're dealing with dry (rather than paste) SLS, wear a good dust mask -- it's a pretty powerful respiratory irritant, and can cause lots of coughing or choking, and even, in my experience, bring on a bad asthma attack that may require hospitalization.  This shouldn't be a problem with Orvus paste, but may be a problem if you're dealing with the dry form of SLS.  Be especially careful to keep it out of your eyes...  it'll sting like crazy, and can cause some damage (if you do get it in your eye, rinse with lots of water -- lots and lots and lots of water!, and call your doctor.)

All this is not to say that Orvus isn't a good detergent, but that it's not quite as simple as "use this like regular laundry detergent and be deliriously delighted with your laundry forever", like a bad TV commercial.  If you use it like a textile conservator would, it's pretty good stuff.  If you start mixing and matching with other products or if you have the wrong tap water for your fiber (few of us have a copious supply of really pure water), you may not be so happy.