# Lye Water Attacking my CrockPot ??



## Gaspar Navarrete (Apr 28, 2015)

Hello everyone,

I have made about 5 batches of soap with this crock pot and there is this stain that I cannot remove.  See picture below.

Has the lye-water reacted with the ceramic surface of my crock pot ?  Is this a safe ceramic surface to use ?

Thanks


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## Susie (Apr 28, 2015)

It's fine.  Mine looks like that after many batches of soap.  If in doubt, run your hand over those spots, rough surface means you have a problem.


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## Gaspar Navarrete (Apr 28, 2015)

It is reassuring to hear that.

For a moment there, I thought that my lye-water was being contaminated by a shoddily made crockpot.

So there is no way to clean this off ?  I've tried all kinds of things.

Thanks


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## Susie (Apr 28, 2015)

I don't use my crock pot for food, so I don't sweat those marks.  I suppose I would start by determining if they are some sort of mineral build up and try something like CLR.

http://www.walmart.com/ip/CLR-Calcium-Lime-Rust-Remover/14574716


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## Seawolfe (Apr 28, 2015)

It looks like hard water deposits to me. If it is hard water, soaking it in a 10% vinegar solution would clean it up.


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## tbeck3579 (Apr 28, 2015)

Seawolfe said:


> It looks like hard water deposits to me. If it is hard water, soaking it in a 10% vinegar solution would clean it up.


 

I was thinking the same thing Seawolfe, but I haven't used my crock for many batches of soap so I was hesitant to say anything.  Hopefully it is cuz it is an easy fix.  Around my sink, faucet, stainless steel bowls used for dog water, pans that I boil water in, etc. I get the ugly spots.  Every so often I take a stronger solution of vinegar and water to go over all the items at the same time using a Scotch-Brite -- soak, scrub, and then do it again if needed -- sparkles like new.


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## LBussy (Apr 28, 2015)

My crockpots are white so I can't see anything but the marks the SB makes.  I have zero issue using my crockpots for food after making soap.  I know the caustic is neutralized, we use a weaker caustic anyway in dishwashers (check the pH of Cascade sometime), and I've filled it with soap and rinsed ... how could that be bad?  Washes right off.


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## Gaspar Navarrete (Apr 28, 2015)

What I did with vinegar was spray it on, let it sit for a bit, and then scrub it off with a scrubby.  I must be doing something wrong here.

Seawolfe, is there a household way to test for hard water ?


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## Seawolfe (Apr 29, 2015)

You can check your city or water department website. I know I have hard water because when I can things my jars get hard water spots on them, my glasses in the dishwaher too. 

Oh and my liquid soap is clear, now that I made it with distiller water 



Gaspar Navarrete said:


> What I did with vinegar was spray it on, let it sit for a bit, and then scrub it off with a scrubby.  I must be doing something wrong here.
> 
> Seawolfe, is there a household way to test for hard water ?


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## FlybyStardancer (Apr 29, 2015)

Gaspar Navarrete said:


> Seawolfe, is there a household way to test for hard water ?



Pet stores with aquarium sections will often have liquid tests that you can use to test for water hardness. It's a simple titration test, with one test for calcium and one for magnesium.


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## galaxyMLP (Apr 29, 2015)

I don't think that is from hard water. I purchased a brand new crockpot for soaping only and this happens after a few batches. My thought is that it is the surface of the enamel on the crockpot is being etched away. It has happened to both of my soap crockpots and not my food one. 

The ceramic is glazed with glass essentially, and lye etches glass (that's why it is recommended to mix lye water in plastic or stainless steel) so I would think it is slowly etching the pot. I tried nearly everything to clean mine. If I scrubbed it really hard, it only got worse. So now I don't worry about it. 

ETA: I have a dedicated soaping crockpot only because I use FO and EO. If I didn't, I would just use a food one.


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## Susie (Apr 29, 2015)

I only have a dedicated soap crock pot because it is old(1986), and the crock does not come out of the base for easy cleaning.  We use the new one for food.  I saved it from being thrown away by adopting it for soaping.  I also bought another one at the thrift store for a buck or two.  

The glaze on my crock is as smooth as glass to my touch, and no discernable marks when being examined with a good light and a magnifying glass.  So I really don't feel it is being etched.  I could be wrong, though.


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## LBussy (Apr 29, 2015)

Glazes are all different, and it's not entirely out of the question that glazes across different manufacturers or even in different lines from the same manufacturer are somewhat different.  

Glazes do contain small amounts of metal oxides of sodium, potassium and calcium, aluminum, iron, lead, copper, cobalt, tin, zirconium, even lead (but not for food these days.)  Nearly any metal you can think of has been used in a glaze (including uranium to make it glow(!?).  All of these have the potential to react with a strong acid or base, so it's not entirely surprising that some glazes etch.  I suspect that glass, which also contains trace amounts of metals for various reasons is also etched for the same reason.  

Contemporary Pyrex is actually tempered soda-lime glass which contains alumina and other metals.  As a matter of fact it contains a surprisingly large amount:  13% Na2O, 10.5% CaO and 1.3% Al2O3.  (Ref: Seward, T. (2005). _High temperature glass melt property database for process modeling_. Westerville, Ohio: American Ceramic Society.)    Older Pyrex manufactured in the US (and reportedly currently manufactured outside the US) was originally borosilicate glass.  The official trademark of the borosilicate product was PYREX, and when the Corning sold/spun off the line the trademark pyrex or Pyrex was used.  It's reported widely (but unsubstantiated) that if you find older PYREX marked glassware it is borosilicate.

Boron is a metalloid, not a metal (as is Silicon).  Metalloids _generally_ are less reactive than metals, so the extension of that is a glass lower in trace metals will be less damaged by strong caustics.

Anyway - the admonition not to use "Pyrex" is because several have shattered (and I think people here have reported that?).  Soda glass has a much higher coefficient of thermal expansion than borosilicate glass (it expands more when heated).  If you combine that property with micro-etching, you have lots of points at which a fracture can start.  remember, "cutting" glass is really making a small scratch (etch) and then using force to break the glass along that line.  Throw in the cooler top of a measuring cup and the intense heat of hydration lower when you add lye, and it's no wonder Pyrex measuring cups have shattered.

All that is to say etching per se is not necessarily bad.  Ceramics do not rely upon the structure of the glaze to provide integrity (where glass is technically 100% "glaze").  If it is etching, I'd give it a definite shrug of the shoulders and go on about my business.


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## galaxyMLP (Apr 29, 2015)

L, I've never thought about the metals in glaze. Might be something interesting to look into. However, sodium hydroxide does dissolve silica (SiO2) the main component of glass. In fact, in LC systems that use silica as a stationary phase (solid in this case), it is recommended that the pH of the mobile phase (liquid in this case) does not exceed a pH of 8 and same with sample injections for the same reason. It happens at a slow rate a room temperature and in dilute solutions, however in the case of making soap, we have strong 9-10 molar solutions of sodium hydroxide heating to 150+ F. 

I have a theory that maybe Susie is cooking her soap on low heat (just a thought!)? My Castile recipe takes 6+ hours on low heat but only 45 min on high heat. This means my cp gets 180-200 F. This would probably be sufficient with the caustic soap batter to cause it to etch. With lower temperatures it is possible that the caustic soap batter will not etch as noticeably and it may take many more batches for it to be visible. 

I also had no idea about any of the history of Pyrex. Very interesting to read about! 

I used to make stained glass and it was always amazing that just a score line (etch) could create such a clean cut with just a tap. I agree its no wonder that the glass has shattered. I also agree that in the case of a CP it shouldn't matter b/c the main bulk of the material is not being etched as is the case with glass. 

Here is an article about glass dissolving in sodium hydroxide. 
I thought it was cool it was from 1957 even though I can't read the whole thing...
http://pubs.acs.org/doi/abs/10.1021/j150553a027


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## Gaspar Navarrete (Apr 29, 2015)

Lets say that the lye was hypothetically etching the glaze on my crock-pot as you described, would this etching leach an appreciable amount of impurities into my soap ?  Etching is a chemical reaction, after all.


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## LBussy (Apr 29, 2015)

galaxyMLP said:


> L, I've never thought about the metals in glaze. Might be something interesting to look into. However, sodium hydroxide does dissolve silica (SiO2) the main component of glass. In fact, in LC systems that use silica as a stationary phase (solid in this case), it is recommended that the pH of the mobile phase (liquid in this case) does not exceed a pH of 8 and same with sample injections for the same reason. It happens at a slow rate a room temperature and in dilute solutions, however in the case of making soap, we have strong 9-10 molar solutions of sodium hydroxide heating to 150+ F.


Interesting.  Hydroxides are quite nasty to a good number of things - I guess that's no surprise.  I'd think that in chromatography *any* change in the solid phase would have significant impact.  So I wonder if that recommendation is because of durability/safety, or just a case of skewed results?



> I have a theory that maybe Susie is cooking her soap on low heat (just a thought!)? My Castile recipe takes 6+ hours on low heat but only 45 min on high heat. This means my cp gets 180-200 F. This would probably be sufficient with the caustic soap batter to cause it to etch. With lower temperatures it is possible that the caustic soap batter will not etch as noticeably and it may take many more batches for it to be visible.


That also makes sense - the Arrhenius and Eyring equations indicate that heat is a component in the speed of many chemical reactions.  If the soap is faster to gel with additional heat, anything that reacts to the hydroxide should be likewise impacted.



> Here is an article about glass dissolving in sodium hydroxide.
> I thought it was cool it was from 1957 even though I can't read the whole thing...
> http://pubs.acs.org/doi/abs/10.1021/j150553a027


I tried my school's library access but that apparently is not a journal to which they are subscribed.  Bummer.

Anyway, I think the takeaway is that if you want your crockpot to stay shiny, don't use it for soap.  I don't think however the culmination of the reaction is something we need to worry about.


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## LBussy (Apr 29, 2015)

Gaspar Navarrete said:


> Lets say that the lye was hypothetically etching the glaze on my crock-pot as you described, would this etching leach an appreciable amount of impurities into my soap ?  Etching is a chemical reaction, after all.


I cannot imagine any way that it could be an appreciable amount.  I suspect the product of the reaction would be Sodium Silicate (waterglass) and the most applicable vehicle by which it could impact us would be by precipitating colloidal particles (soap) - and I doubt the micro-minute amounts would do anything at all, even if you let the reaction continue for several years.


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## galaxyMLP (Apr 29, 2015)

Gaspar Navarrete said:


> Lets say that the lye was hypothetically etching the glaze on my crock-pot as you described, would this etching leach an appreciable amount of impurities into my soap ?  Etching is a chemical reaction, after all.



Not an appreciable amount by any means. Plus, even if it was, it would still be harmless as you are producing sodium silicate which is pretty harmless stuff.  its nothing to worry about. Sorry I geeked out and got all sciencey on this!

ETA: Lol, L beat me to it!  guess its just a confirmation! Totally agree with L.


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## LBussy (Apr 29, 2015)

I find the quickest way to get the right answer online is to give the wrong one, so I'm never shy about throwing out a guess.


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