[Cob] suds & Soap Scum & Alum/Soap waterproofing

[littlehouseantiques at att.net]

Ah, soap semantics!

If you define soap as being made from materials found in nature 
and detergents as being made from ingredients not found in nature 
and therefore synthetic, then YES I'm using a synthetic detergent 
as an extender for my paints.  However one could argue that even 
'natural' soaps are synthetic because the process of making soap 
contains at least one and sometimes two 'synthesis steps' (when 
you render the fat to remove the impurities from it AND when you 
heat the lye/water solution to help dissolve the fats or oils 
into the mix).      

Jon says that "modern detergents have SUDSING AGENTS added in" 
but what he really means (I think!) is that soap is an anionic  
surfactant whereas detergents contain both anionic as well as 
nonionic surfactants.  Natural soaps work poorly in water 
that contains mineral salts such as calcium (Ca), magnesium 
(Mg), iron (Fe) and manganese (Mn) or "hard water" because 
the mineral salts react with soap to form an insoluble 
precipitate known as soap film or scum.  This is one of the 
reasons modern detergents were produced to begin with.  
Detergents that contain more than one surfactant are less 
sensitive to the mineral salts in hard water and they don't 
form that nasty ol' "soap scum".    

So why does a detergent SUDS up better than a soap?  Well, 
because when natural soap is added to hard water, some of the 
soap is used up by reacting with hard water minerals to form 
the soap scum or film & this reduces the amount of soap 
available...so less suds!  

Sorry to go on at such length about soap of all things but I 
think I finally now understand why a natural SOAP used in 
conjunction with Alum would work to repel water--because when 
you use a natural soap AND hard water, you are combining 
mineral salts and producing that lovely 'insoluble precipitate' 
that we all know and love--SOAP SCUM!  

Think about it!  Soap scum is VERY water resistant and practically 
takes a jack hammer to get off of some surfaces.  (We use Ivory 
Bar Soap and I actually have to use a very fine grit sandpaper to 
remove the scum from our fiberglass shower enclosure as nothing 
else will even touch it!)  

Still not sure what role the Alum plays in conjunction with the 
soap, perhaps it has more to do with the water (in other words 
used as a flocculent to settle the silt?)

I'm rather intriqued by the thought that soap scum may actually 
have a POSITIVE use!  And since I can't seem to find anybody 
with hands on experience or any specific alum/soap recipes, seems 
like some good old fashioned experimenting is in order.  

Wandering off to don the lab coat now....

Kathy



-------------- Original message from Jon Kerr : -------------- 

> Another point about this thread is that modern detergents have SUDSING 
> AGENTS added in, and BTW so does a lot of mass market beer. The reason 
> proper soap is usable for waterproofing would be the oil repelling 
> water. 
> 
> Jon 
> 
> >a) unless you're using Dr Bronner's Peppermint Soap for your dishes, 
> (o.k., his almond, or lavender count too), you're probably using 
> DETERGENT. Even the Bronner Sal Suds is a detergent. I don't know 
> much about detergents. Soaps are made with a fat or oil and a strong 
> base like lye by definition. And there may be a big difference between 
> soap and detergent in the context of traditional waterproofing. 
> 
> ............... 
> 
> >Kathy wrote: 
> Uh, no, I don't think so. I use regular ol' liquid dish soap in my 
> acrylic water based paints (to extend drying time) and none of it 
> has ever "re-suds up".