Lye Mixing Problems

[netispguy]

Hi all,

I am a newbie here, so I apologize if I am posting this incorrectly.

I encountered a problem recently that maybe someone in this forum may have seen in the past. I mix large amounts of NAOH in a big tank that lasts us about 4 months or so. In the last batch I mixed 50 lbs of high grade NAOH to about 150 lbs of distilled water. Usually I let it gas-off for a while then stir it a bit before covering it up and allowing it to cool overnight. When I did the batch this time I was in a major rush to pick up the kids and I did not stir it as much as usual.

When I checked on the solution the next day I noticed that a hard solid white "crystal" like layer had formed on the bottom of my NAOH tank... and it seems to be very stubborn and not wanting to go away that easily. Since I have what appears to be undissolved NAOH at the bottom of the tank, I am afraid my ratios are messed up and I don't trust it at this point.

Has anyone seen this before and is there a solution (like maybe heating it up) or I am going to have to empty the tank and "carve" it out?

Thanks in advance for any advise or comments.

-Scott

 

[heart of dixie soap co]

lye soloution problems

i've never made that much in advance before..
questions-is this a new batch of lye? is it pellet or flake? did you change brands?

on a smaller scale this has happened to me before when i didnt stir or agitate it thoroughly and the undisolved lye hardened at the bottom. this was easily fixed by a little more stirring. how much lye is caked on the bottom?

monet

 

[Soapmaker Man]

When you say "newbie" do you mean to this forum, or to soaping. That is a lot of sodium hydroxide solution. Only big producing soap companies use sodium hydroxide mixing barrels.
You are mixing at a 33% lye solution rate, which is normal. At a 33% rate, you should not have any build up of lye in the tank. I make up a gallon of 50% lye solution at a time, and never have any build up in my HDPE container, even at 50%.

Paul

 

[netispguy]

lye soloution problems

Paul,

I am new to this forum, not to soap making. Sorry about the confusion.

To be more specific, we use about a 39%-40% solution (%w/w) of lye to water. We like to supper-fat and this is for an oil mixture that has about a 6% discount. In general a 1/2 batch of lye for us is 50lb NAOH : 124 lb H20. Our tank will hold twice that and we like to say our ratio is 1:2.48 or so... So making the math simple, for every 100 lb of lye, we use about 240 lbs of water or between 39-40% solution.

We do produce a lot of soap, but I would not call us a big soap company... yet... but we did start off at a gallon at a time. Each and every bar of soap we produce is 100% handmade using only cold process and only natural essential oils (i.e., no fragrance oils at all).

The lye issue is very strange. In response to Monet's reply, I purchase high quality "fine Pellet" grade NAOH from a chemical supplier in the San Francisco Bay area. I buy 50 lb bags in 200 lb quantities... I need to have an MDS on the front seat when I transport it back to our workshop. I also purchase a lot of Citric Acid from them as well. They supply a lot to the pharmaceutical companies in N. CA. and the quality of their products is very good.

Getting back on track, I put in about 124 lbs of distilled water into our tank, then I fully suited-up with face mask and proper respirator, long sleeves and gloves. I turned on the hood and make-up-air system, lifted on 50 lbs bag up and using a box knife, made a 6 inch slit at the top. I then poured in all 50 lbs without stopping. After putting the empty bag in the sink (which we will rinse out before tossing in the trash), I placed the lid back on. Normally I give it a number of full stirs, but I did not this time. I did one check about 10 minutes later and the temperature was up to about 185 degrees (normal) and that was it.

The next day I found about an estimated 1/8" layer of white on the bottom of the tank... which was "hard as a rock" I tried stirring and was able to get some additional reaction (as the temperature rose to about 115) but most of it still remained on the bottom and short of smashing it with a pick and sledge hammer, that is how I left it at the end of the day... uggg

Thanks for the comments so far!

 

[IanT]

woahh.... way out of my league lol... wish I was in that league though ...one day....one day

 

[donniej]

I only use about 2 pounds at a time so you're still way out of my league. But I've often had a hard time getting it to dissolve. I can't say that I'm surprised that a bit hardened up on you. If you can heat or bang on the bottom of the tank, or even blow compressed air through the bottom, I bet you can break it up pretty easy. Be careful with the compressed air though, I'm sure that would easily kick up a pretty wicked caustic cloud.

In the future it might be a good idea to put a stirrer on the tank. I use a drill with a paint mixer. You might be able to modify a drill press or even a standing mixer to do the same.

 

[netispguy]

Let me add, just in case it is not clear, I have a tank with about 10" of liquid siting on top of this hard layer of what appears to be hard white crystal substance.

We have the heater on now and are going to bring the temp to about 150 degrees F to see if it helps to break up the layer.. plus I am going to get a large rod/screwdriver and see if I can chip away at it.

It these two methods don't help, I am going to have to drain the tank (which would be about 15 gallons) and fully "dig" out the substance.

I cannot trust the concentration of the solution at this point since there seems to be a considerable amount that did not dissolve...

... what a mess :cry:

 

[Soapmaker Man]

Sounds like you had a really bad batch of caustic soda to me. Bummer.
I bought 250 pounds a few months ago, and so far, it is fantastic.

 

[jadiebugs1]

in comparison....I usually am mixing about 3oz. of lye in about 8oz. of water in a mason jar ( :roll: ), but the SAME exact thing happened to me once....instead of slowly pouring in the lye and stirring, I put it in all at once and thats what happens!....turns to a rock in the bottom. I was able to chunk it out with my spoon and stir, stir, stir, but that's what it sounds like to me, your not stirring as much as you usually do was my guess, the problem......
bet 'cha won't do that again, huh? :wink:

 

[netispguy]

okay... I was inspired by Jadiebugs1 reply... and I think we have learned a lessen... I now have good news.

So, after reading jadiebugs1 reply I went to the lye tank (which I had now heated to about 150 degree F) and took a long screwdriver and hammer and carefully forced the tip down into the "rock layer". I was able to get to the bottom of the tank, but as I tried to use the screwdriver as a lever, it was not strong enough and started to bend; however, I was now motivated to at least chip some more of it away. At this point I ran over the local Home Depot and purchased one of their large "wrecking" bars, which is really just a large pry used to remove roofing material, etc. They only come in black and yellow...

Back at the shop I fully washed off the bar, grabbed my hammer and went to work. After a number of pretty good smashes with the hammer I was able to break through the "rock layer" and get to the bottom of the tank. First on my list was not to break the tank and have a haz-mat problem. Second, I noticed that the layer was almost 3/4" thick. I repeated this process about 15 times at various locations within the tank and was able to separate some pretty large irregular sized "disks" of hard lye.

Once again being motivated by Jadiebugs1's advice, I "stir, stir, stir" and the solution starting turning a milky white and I started to smell the lye gas and see bubbles... I grabbed my respirator (which hangs next to the tank) and continued to "stir, stir, stir". I could see the disks moving around in the tank. After about 10 minutes I stop stirring and went to help someone who was making some bath-bombs at the other side of the shop. 30 minutes later I went back to check on the tank and much to my surprise, it was totally clear with NO solid lye to be found. I did have some minor contaminants floating on the top as a result of the hammer and bar activity, but other than that, everything looked normal again

I was able to speak with a chemical expert in Los Angeles later in the day and he told me this is common in large lye preparations. He told me that in large industry where they might do thousands of pounds at a time, they have special vats that have built in stirring capabilities and they still need to go in and "scrape out" the vats from time to time. He further explained that just like pouring salt or sugar into a glass of cool water, most of it will fall and sit at the bottom unless you provide additional energy (stir) to force the bonds in the atoms to break down and form into a solution with the water. He also told me it is VERY important to re-stir NAOH solutions each and every time you use it IF you let it sit or store it more then 24 hours, as crystals could form that might be invisible or hard to see. He then said "now, all of you soapers do use a good hydrometer to test your lye solutions, right?"

Thanks for everyone's help and one last thing... the bottom 10 inches of the bar I purchased from Home Depot is now bright "silver", with no black or yellow color to be found :!:

-Scott

 

[donniej]

Glad to ear you got it worked out and didn't lose the batch.

A stirring device would be a good idea. KOH comes in easy dissolving flakes which is why alot of BioDiesel guys use it instead of NaOH. Unfortunately it only makes liquid soap.

And lye will definitely eat a lot of paints, plastics, etc... Mix it with methanol (again for BioDiesel) and you'd be amazed how many of your tools you can melt

 

[jadiebugs1]

Glad I could help! And thank YOU for the much needed chuckle I got when you said you went to buy a "wrecking bar". How funny! Determined little soapers we are, aren't we?? :wink:

Glad it all worked out!

 

[cambree]

okay... I was inspired by Jadiebugs1 reply... and I think we have learned a lessen... I now have good news.

They only come in black and yellow...

Thanks for everyone's help and one last thing... the bottom 10 inches of the bar I purchased from Home Depot is now bright "silver", with no black or yellow color to be found :!:

-Scott

I guess the black & yellow paint are now a part of the soap, if not already floating on top of the lye solution.

I was following this thread and found it to be very informative! Inspirations can be found in many places. So glad to hear netispguy had a good ending too.

 

[puntacocosoaps]

Rule of thumb. Try to get the lid back on as fast as you can and leave it on. Try not to let the gases escape.


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