STPP

[foraloysius]

Sorry my wrong, it was not phosphates but Sodium Metabisulfite.

 

[sudsmaster]

Laundress is correct: while milder than the usual sodium carbonate (washing soda) in most American laundry powders, STPP is still alkaline and therefore can degrade protein based fibers like wool or silk. For such fabrics a neutral detergent like Woolite is recommended.

 

[mrboilwash]

IIRC back in their days powdered detergents for wool and silk were full of phosphates but also buffered with an acid to achieve a milder but still slightly alkaline pH.

Just checked some of today`s wool wash products (Coral Wolle und Seide, Perwoll Wolle und Feines, Sanso, Woolite) and can confirm all of them, the powders as well as liquids have a pH range of 8 - 8.5
Not exactly neutral but still very mild alkaline, some inferior bar soaps can be more aggressive in pH.
Contemporary Sanso powder is even loaded with washing soda but also buffered to a milder pH of course.
I remember that liquid Perwoll used to be slightly acidic according to the msds at some time ago, but for some mysterious reason this isn`t the case anymore.

So if someone desperately wants to play chemist on washday, yes it is possible to use harsh chemicals like STPP or washing soda even for the most delicate things like wool and silk as long as the pH is properly buffered with an acid.
I wouldn`t dare doing this myself because I have no way to check the pH of the finished product accurately. I don`t think litmus paper would do in this case.[this post was last edited: 8/18/2019-13:02]

 

[bladeandstone]

STPP with Borax and/or Sod Carb?

Are there occasions where one would recommend including STPP along with either Borax or Washing Soda or both?

 

[DADoES]

 
I've added STPP to every wash load for 10+ years, with any/all other additives ... chlorine bleach, oxygen bleach, or Biz powder.  Have never used borax, or washing soda (sodium carbonate) directly other than whatever amount it may be present as a "filler" in other products.  If I understand correctly, sodium carbonate is primarily used as a water softener for laundry ... but it generates a precipitate.  STPP does not (it's non-precipitating) so is a better choice, and washing soda shouldn't be needed with it.

 

[mrboilwash]

Not a chemist here but if you add a weaker base substance like STPP to a stronger base like a heavy duty washing powder it would add up the total pH, wouldn`t it?

And aren`t aluminum washer parts susceptible to strong bases?
And don`t detergent manufacturers therefor add silicates like water glass, another strong base but it also forms a protective coating on metal washer parts thus acting as corrosion inhibitors.

I wonder if there really are no negative effects on washer parts to expect in the long run if STPP is added to any detergent but the silicates to other alkali ratio is not altered accordingly.
I mean if detergent is mixed with STPP you end up with a higher pH and at the same time you weaken the corrosion inhibitors of the detergent. Not an ideal combination. Or have I missed something?

 

[ultralux88]

Interestingly, I’ve just recently started using Bubble Bandit... we have hard water and have yet to install a softener, so it’s been challenging. The dishwasher was getting coated in deposits and scale, and the washer was also. Both were also just full of dinge, and it was frustrating and kind of disgusting. My thinking here was, if the machine is coated in this nastiness, I just have the feeling the dishes and clothes were too. I had the chance to add some TSP that was being used to clean a cement floor to a load of white ‘just I see’, and they care out the cleanest and whitest I’ve ever seen! So I decided that detergent with STPP in it would be good, and so far it has actually cleaned the clothes, the washer, the dishes and the inside of the dishwasher is completely clean and new looking again. I also notice that I can just load the plates into the dishwasher with absolutely no rinsing or even scraping, and they come out completely clean, dry, and spot free. Although the first couple weeks of dishes were very spotty, this stopped as soon as the dishwasher was cleaned inside.

 

[sudsmaster]

add a weaker base substance like STPP to a stronger base

No, adding STPP to a stronger base like washing soda would not increase the pH (make it even more basic). That's because these chemicals have a pH point about which they like to sit. STPP's pH point is lower than washing soda's, so it might well reduce the pH of the resulting mixture, albeit probably only slightly. In more technical terms, STPP will try to buffer the solution to a lower pH.

One time a while ago I tried taking a warm bath with STPP as a sort of bath salt. The water felt wonderful and I came out feeling quite refreshed.

 

[mrboilwash]

Thanks for clearing this up

 

[tomturbomatic]

Food Grade STPP, not the stuff from China, is used in dental rinses. I use it with toothpaste for cleaning my teeth. STPP added to a bath will eliminate bath tub ring. We used to use Calgon for that. It was neat to hold it in your hand and lower into the water for an unexpected reaction.