Robert Goodman

You're asking whether you can add it directly to your bath to make it foam? Certainly you can. It won't foam as efficiently as it would if you included even a small amount of a foam stabilizer, but it does work. These guidelines about the percentage you can include in a preparation may safely be ignored. You'll be achieving a certain concentration of SLSA in your bath water. Whether you get there by dissolving a little pill of pure SLSA (well, as pure as it comes; there'll always be a substantial percentage of sodium sulfate and other process "leftovers" in it) or a larger mass of mixed powder of SLSA with other stuff is immaterial. Nobody asks what the safe limit of soap is, right? You can use a solid cake of soap. But the makers of other surfactants, thru the CIR, have set limits based partly on testing and partly just conservatism; they have not established that higher concentrations, used properly, are unsafe. The thing about SLSA, though, is limited solubility. I seem to recall you could get only about 4% solution in water at room temperature. This is why it's not very popular in liquid formulations. You might be able to increase that percentage somewhat with other surfactants in the solution solubilizing it.

Also I could suggest that if you're looking for another powdered alternative to SLSA, there's SLSS: disodium lauryl sulfosuccinate. It's similar to SLSA in its solubility and the type of foam it produces, and may be slightly milder. I used SLSS to make an experimental tablet form of my bath foam.

Well, what are those customers' options? Why assume customers would be turned off by your ingredients as opposed to those of other products they might buy? However, it should be noted that some products deliberately add ingredients for "label appeal" in amounts that would be too small to have any effect -- or maybe that would be expected to have a useful effect in shampoo in any amount!

Usually less SLS would be required than SLSA. However, I would not be put off from using cocamide DEA (coconut diethanolamide). The "possible carcinogen" was a total fluke result in some screening in rodents that I as a cancer researcher would not give credence to. There are other reasons to prefer other ingredients to fatty diethanolamides -- various substitutes are lower in eye sting and skin irritation, and waterlog skin less -- but in some applications like bubble bars cocamide DEA may still be the best choice. These fatty diethanolamides serve as foam stabilizers, and allow you to use much less primary foaming agent (SLS or SLSA or other) than otherwise. So even though the fatty diethanolamides are much more irritating than most surfactants on a mass basis, in actual use they're reducing the total surfactant concentration and thus irritancy in the product overall. In a liquid product there are other foam stabilizers that are milder still, but cocamide DEA is very convenient to mix into a solid product, expecially a tablet, in the amounts useful in such a product. It is possible, though not as easy, to make a tablet with other foam stabilizers that come in water solution, such as alkamidoproyl betaines, and if you're making a combination fizzie-foamy it's practically impossible to be using that much water. (I don't recommend combination fizzie-foamy tablets, but they're in common use.) Without the cocamide DEA, you'll need more SLS or SLSA to make the foam last as long, and then you're getting a "soapier" bath than you might want; you want the bath to have foam on top to be played with, not to be detergent enough to do laundry! A typical formula would use a weight ratio of, say, 8:1 of the anionic surfactant to the cocamide DEA.