What cycle to add STPP

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baboonfury

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Hi - I have a modern LG HE front loader machine and have begun adding STPP as we have very hard water where I live. I've learned a lot from the forums but am a bit confused as to when the STPP should be used in the wash. Right now I have it added to the pre-wash cycle which is really only STPP. Should I be adding it here or am I adding an unnecessary step as it sounds like a lot of people just mix it with their detergent and use it in the main cycle. Also is there any guidance on the ratio of STPP to detergent?
 
 
STPP functions as a water softener and detergent booster (although it's neither bleach nor enzymes).  It should be added to / with the detergent.  Less common usage but it can also be added to the (last) rinse if desired to treat the water, dissolved in warm water and placed into the liquid softener dispenser.  Calgon water softener powder was years ago sometimes touted as a rinse additive.
 
Main wash here also.

I view the pre-wash part of a wash cycle as being useful for heavily soiled loads, like gardening togs with lots of dirt, or dirty diapers. There the main function of the pre-wash would be to remove this excess dirt before a detergent is added.

I suppose one could add STPP to the rinse cycle if one has extremely hard water, in an effort to reduce hard water mineral deposits in the final rinse. The water here being on the low/medium side of hardness, it's not something I've tried. But... I might try it on the next load of bath towels to see if it makes any difference.
 
When laundering with soap (just that, not detergent), with hard or even moderate water it was often advised to add packaged water softener to wash and first rinse. This would bind hard water minerals to keep scum and other muck away from laundry.

Hopefully by second rinse much of soap had been already removed so chances of scum forming was less.

Detergents aren't bothered by hard water (one simply adjusts dosage according to local water hardness), so in theory adding water softener to rinse isn't required. See discussion in another thread elsewhere on forum about importance of rinsing when doing laundry.

When using detergents making water overly soft (as in using too much packaged water softener, especially phosphates) can cause issues. Again the surfactants used in detergents aren't as bothered by hard water minerals compared to soap. Thus rinsing shouldn't be as difficult because unlike pure soaps introduction of fresh hard water won't cause detergents to bind to wash.

If one is attempting to strip laundry, then phosphates can be used in both wash and rinse, but then you don't use detergent or soap.
 
Well, I added about 1 tsp to the rinse compartment for the last load of bath sheets in the Neptune 7500. The only problem is that the STPP didn't completely dissolve in the cold water rinse. Next time I guess I'll have to pre-dissolve some in hot water first, then add that. I've though of premixing some STPP solution in advance, but that might not work as well since STPP isn't permanently stable in water. We'll see. Couldn't hurt to try.

The result from the partially dissolved STPP is a bit ambiguous. The bath sheets are not harsh, but not as soft as some that I added a bit of softener to previously. The limited STPP amount in this last try might be the issue there. We'll see!
 
While not highly alkaline as washing soda, never the less STPP does raise pH of water. On its' own there's nothing particular about phosphates that would result in softer or fluffier laundry.

Absence or low amounts of other harsh substances like washing soda, sodium hydroxide, etc.... when using phosphates as main or only builder would leave things feeling smoother I shouldn't wonder. That and of course no matter what one does when using soap for wash day trace amounts will always remain regardless of rinsing. That's the "built in fabric softener" effect soap laundry products were always touting.
 
I wouldn`t recommend to add anything alkaline to the last rinse not only because it can give clothes a stiff and harsh feeling but mostly because the alkali would make clothes much less skin friendly.
There`s a reason why nearly all additives designed for the last rinse are acidic these days.

I know it has been done in the past when soap was still widely used for laundry to prevent the formation of soap scum in hard rinse water, but I`d consider it as some sort of a compromise. Means fighting one evil with another one.
Remember the no rinse detergents from the same time frame? It was all about cutting corners and of course it had a bunch of disadvantages.
I you wanted to do it properly you`d have to follow the phosphate rinse with a sour rinse or at least a clear rinse but none of it makes sense anymore unless if you still wash with pure soap in hard water.
Phosphates added to the wash cycle along with detergent on the other hand might still be helpful as a wash booster or as a water softener to cut back the amount of detergent used.
 
Next to last rinse...

Next to last rinse is a bit problematic in that it would require manual intervention (and watching the cycles) to catch the washer at that stage. And, admittedly a bit more of a chore with a fully automatic front loader like the Neptune than with a top loader. I suppose.

I'll give the last rinse/STPP another try in the Neptune (after pre-dissolving it in warm water) and see if that works.

PS: why does my international spell checker want to substitute "per-dissolving" for "pre-dissolving"? Oh, wait, it had switched itself to UK mode. Darn it all. I don't know anyone who says "per" in stead of "pre". Or maybe it's just written "per" in Old Blimey but pronounced "pre"?
 
The real question you will need to resolve is if it is needed in the rinse. If you add it to the wash, you are going to be able to use less detergent to begin with and the solution of the detergent and STPP will rinse out of the clothes easier because of the presence of the STPP.

I wish you success.
 

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