# Food grade lye vs technical lye



## leillani (Mar 3, 2010)

Hi!!!! Im new to soap making and wanted to know if food grade lye and technical lye make a difference in soaps... thanks


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## jennikate (Mar 3, 2010)

Not really difference is price you pay.


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## xyxoxy (Mar 3, 2010)

I don't think the soap knows any difference. Your pickles and pretzels and lutefisk might though.


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## IrishLass (Mar 4, 2010)

I've used both and can say that they both make great soap without any detectable differences that I ever noticed. 

IrishLass


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## leillani (Mar 4, 2010)

Thanks!!  , bought the tech since its cheaper...


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## cleanwater (Mar 4, 2010)

I'd be curious about contaminants, though as a chemist I'm not actually sure which kind would be purer...


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## cheesenoodle (Nov 25, 2011)

cleanwater said:
			
		

> I'd be curious about contaminants, though as a chemist I'm not actually sure which kind would be purer...



Food grade lye has tighter restrictions on things like heavy metals such as lead than technical grade does.  That's why I'd be worried about using tech grade..


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## falldowngobump (Nov 25, 2011)

I've used both, with no differences at all.  I use tech grade all the time now. If there are differences no one could tell, including me.


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## hbmo (Nov 29, 2011)

cleanwater said:
			
		

> I'd be curious about contaminants, though as a chemist I'm not actually sure which kind would be purer...



There are three methods that commerical lye is made through eletrolosis of salts

Mercury cell process (also called the Castner-Kellner process); sodium ions are reduced to sodium metal, which forms an amalgam with a mercury cathode; this sodium is then reacted with water to produce NaOH. There have been concerns about mercury releases, although modern plants claim to be safe in this regard.[5] Does leave mercury traces


Diaphragm cell process; uses a steel cathode, and the reaction of NaOH with Cl2 is prevented using a porous diaphragm, often made of asbestos fibers. In the diaphragm cell process the anode area is separated from the cathode area by a permeable diaphragm. The brine is introduced into the anode compartment and flows through the diaphragm into the cathode compartment. A diluted caustic brine leaves the cell. The sodium hydroxide must usually be concentrated to 50% and the salt removed. This is done using an evaporative process with about three tonnes of steam per tonne of sodium hydroxide. The salt separated from the caustic brine can be used to saturate diluted brine. The chlorine contains oxygen and is purified by liquefaction and evaporation.[6][7] asbestos has been known to be cancer causing 


Membrane cell process; similar to the diaphragm cell process, with a Nafion membrane to separate the cathode and anode reactions. Only sodium ions and a little water pass through the membrane. It produces a higher quality of NaOH. Of the three processes, the membrane cell process requires the lowest consumption of electric energy and the amount of steam needed for concentration of the caustic is relatively small (less than one tonne per tonne of sodium hydroxide).[6][8]


It is obvious only one is abcent of dangerious levels of toxins. The membrane cell process.

The first using mercury has been the blame of high levels of mercury in frutose sugar which uses caustic soda in its making. 
You would think in these times of awareness that the third and most safe methods of collecting lyes ,membrane cell method from salts would be the perfered way. But from my studies so far. Only 13% of the lye supplies, both sodium and potassium hydroxcide ,are made using this method. Due to the expense of factory equipment needed to upgrade to this safer method.


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## soapbuddy (Nov 29, 2011)

NaOH is not the same as KOH. I buy whichever lye costs less.


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## hbmo (Nov 29, 2011)

soapbuddy said:
			
		

> NaOH is not the same as KOH. I buy whichever lye costs less.



Not according to this website
http://chemindustry.ru/Potassium_Hydroxide.php

Production. 
Almost commercial potassium hydroxide is manufactured by electrolysis of aqueous solution of potassium chloride KCl or potassium carbonate K2CO3: 

2KCl + 2H2O → 2KOH + Cl2↑ + H2↑ 

There are three technological processes most commonly used for KCl electrolysis: 

Mercury cell electrolysis. Titanium anodes are located above a liquid mercury cathode in the electrolysis bath with a solution of potassium chloride. When an electrical current is applied, chlorine is released at the titanium anodes and metal potassium dissolves into the mercury cathode forming an amalgam. Dissolved potassium is then reacted with water releasing hydrogen to produce KOH. There have been concerns about mercury releases, although modern technologies claim to be safe in this regard. This method consumes vast amounts of energy. 

Diaphragm cell method. In this route a porous asbestos or polymer diaphragm is deposited on an iron grid cathode preventing the chlorine forming at the anode and the potassium hydroxide forming at the cathode from re-mixing. The potassium hydroxide must usually be concentrated and the salt excess removed. This is done using an evaporative process. Potassium hydroxide produced by this method is contaminated with potassium chloride; 

Membrane cell method. - similar to the diaphragm cell process. The electrolysis cell is divided into two by a ion exchange membrane. Only potassium ions and a little water molecules pass through the membrane. This method is nearly as efficient as the diaphragm cell and produces very pure potassium hydroxide but requires very pure potassium chloride solution. Of the three processes, the membrane cell process requires the lowest consumption of electric energy and the amount of steam needed for concentration of the end product

This one shows how sodium hydroxcide is made 
http://www.ausetute.com.au/chloralkali.html
has more basic detail


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## IrishLass (Nov 29, 2011)

NaOH is used for making solid or hard soap, and KOH is used for making soft soap.


IrishLass


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## carebear (Nov 29, 2011)

soapbuddy said:
			
		

> NaOH is not the same as KOH. I buy whichever lye costs less.


I assume you mean you buy whatever NaOH, technical or food grade costs less.

KOH can also be called lye.


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## carebear (Nov 29, 2011)

hbmo, I don't get your point. Please explain.


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## hbmo (Nov 30, 2011)

carebear said:
			
		

> hbmo, I don't get your point. Please explain.



Well basically in reference to the concern about the differences between food grade and industrial lye's ,and their purposed safety. What I discovered above, is yes not all lye is created equal. And viewing the different methods of processing commercial lye's from salts. It is obvious the concern should center around how the lye was made. The membrane cell method would be my pick.


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## Fragola (Nov 30, 2011)

To my knowledge, asbestos is only dangerous when inhaled (or ingested). I don't have any problems with asbestos in soap.

I assume it's not very difficult tracking down the purchased lye back to the producer, and finding out the manufacturing method.


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## hbmo (Nov 30, 2011)

Fragola said:
			
		

> To my knowledge, asbestos is only dangerous when inhaled (or ingested). I don't have any problems with asbestos in soap.
> 
> I assume it's not very difficult tracking down the purchased lye back to the producer, and finding out the manufacturing method.



Yeah the easiest way would be to discover the manufacture that makes it with the method you approve, and ask who thier distributors are. That is how I trace anything I am looking for. I always tend to go to the head of the source. Knowing tinkle down info can be tainted. Everyone wants to make a buck. Cant blame them.


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## soapbuddy (Nov 30, 2011)

carebear said:
			
		

> soapbuddy said:
> 
> 
> 
> ...


Exactly.


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## carebear (Nov 30, 2011)

it's just soap.


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## Annavlz (Jul 30, 2014)

I bought some caustic soda online, dont know what kind of it, it was packed into a small (1kg bottle ) for me with only one lable "sodium hydroxide". I used it with no problems, never had a zap while testing sope the next day after making.
Then I bought some in a big bucket and as trice as cheaper at the cash&carry shop, with a lot of words about safety and uses and a number >98%. Every batch I did since is a total disaster: if I dont put it in the fridge it is overheated and leaking with lye, if I stop gelling it is ok but has zap for 2 days already. 
I use my usual recipes, I checked the amount of lye in different calcs.
The last batch I made I overfat it 10% but it still zaps very very strong. 
So what can be wrong? And what can I do with it?


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## seven (Jul 30, 2014)

what does it says on the bucket? is it pure sodium hydroxide and nothing else? my initial reaction is botched lye. can you call the shop and ask them about it? the >98% is normal me thinks, as there is no 100% purity for lye as far as i know (well, maybe there is, but the high grade ones).


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## cmzaha (Jul 30, 2014)

Please keep in mind soap can zap for 72 hrs if being poured at a very thin trace. Also make sure you scale is correct and has new batteries. I have calibration weights for checking my scale for error. I am thinking you have other issues going on other than the lye itself. I use tech grade lye from a chemical house that is 98% on the bag. Without looking up the msds I remember it stating not less than 99% for my last bag. 50# bags cost me less than $0.94 per lb and I don't have to pay shipping. Not much point in paying the price of food grade when it is going in soap


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## CanaDawn (Jul 30, 2014)

Annavlz said:


> I bought some caustic soda online, dont know what kind of it, it was packed into a small (1kg bottle ) for me with only one lable "sodium hydroxide". I used it with no problems, never had a zap while testing sope the next day after making.
> Then I bought some in a big bucket and as trice as cheaper at the cash&carry shop, with a lot of words about safety and uses and a number >98%. Every batch I did since is a total disaster: if I dont put it in the fridge it is overheated and leaking with lye, if I stop gelling it is ok but has zap for 2 days already.
> I use my usual recipes, I checked the amount of lye in different calcs.
> The last batch I made I overfat it 10% but it still zaps very very strong.
> So what can be wrong? And what can I do with it?



Could be whatever the other 2% is that is causing a problem?  Does it give any indication what that 2% is?  It's for sure sodium hydroxide 98%?  

I had trouble with a new lye causing overheating, but nothing like as bad as what you are describing, and soaping at a lower temperature of oil and lye solution worked just fine to solve it for me, but it sounds like you have another issue going on.


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## Annavlz (Jul 30, 2014)

I



I think there is nothing more than caustic soda in it, as you cant have 100% spirit in the bottle. There is always will be some water from the air. 
I had a thought about the scales, it is my next test to do. ( but if it weights rong it should do it with all the ingredients so proportions would be the same, I think. On the other hand with low battery it could just gone crazy)
The batch I made 3 days ago with no gelling is still zapping, but not so strong already.
I will continue to experiment and will post results later))


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## CanaDawn (Jul 30, 2014)

a screwy scale won't necessarily be out by proportion, so it could definitely affect the outcome badly (rather than just making you make a slightly smaller or larger batch than planned)


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## Annavlz (Jul 30, 2014)

I think I solved this problem. It seems that quality of lye can really differ from producer to producer. 
This one I switched to just works longer. May be it works as usual because I always read about zapping and had never experienced it myself with the previous lye. And the first one was really good- quick and easy. But when the difference in price is so huge, 6 dollars and 14 dollars for the kg, I'm ok to wait a little bit longer than usual (for me))))
Thanks for empathy, everyone. It helped to keep going))

Resume: when you open a new bottle of lye, especially from another producer, test it on a small simple batch and give it time.


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