Lye Master Batching Advice Wanted

Long story short: A group of ladies joined me to make soap for the shoeboxes for Operation Christmas Child. We succeeded in making about 100 bars in one morning; our goal is 300.

In my preparing, I searched this site to find ideas on how to master batch the lye water, and I opted for pouring it in to safe plastic buckets to cool It did not cool fast enough, even though I put it all in the freezer once it off-gassed. (I went there an hour early to try to get it all made and cooled.)

I am so uncomfortable usng the plastic buckets... And it didn't seem to allow cooling much... It looked like white floaters in the water too... plastic?... I cannot afford to go buy big glass somethings to put the lye water in to... Nor am I willing to go at 6 in the morning to make lye water... But I do have 1/2 gallon mason jars (but with those metal lids they come with).

Could I make the lye water in the mason jars the night before and put plastic wrap or something over the lid and shut them, transport them? Or will it eat through and ruin the lye water..........

Help? Ideas?

This Saturday is our second soaping day to make 100 more. :think:
-LisaB

A few floaters are sodium carbonate (washing soda) and not a problem. Just soap with the lye solution -- no straining is required.

edit: If your plastic container was used before to hold something fatty, it's also possible the floaters in the lye solution are flecks of soap created when the lye reacts with the fat residue. Also not a problem, and no straining required.

Please don't use glass. I would collect some sturdy plastic jugs with secure caps -- milk jugs, detergent bottles, etc. Anything made from these plastics -- PP (polypropylene), HDPE (high density polyethlyene), or LDPE (low density polyethylene). Absolutely do NOT use the clear plastic drink bottles (PET or PETG, polyethylene terephthalate). It seems the PE in PETG should be fine, but PETG plastics do NOT work with NaOH.

Because most of these jugs have small openings, I'd make the masterbatch solution in a plastic pitcher (again check the type of plastic) so you can be sure to get the NaOH properly dissolved. Then pour the lye into your jugs using a plastic or stainless steel funnel to protect against spilling. Don't fill the jugs to the brim if possible. The lye solution will be easier to pour without dripping if the jugs are only, oh, about 3/4 full.

Lightly cap the jug while the lye solution is hot, so any pressure can escape but air and other contaminants can't get in. Let the lye solution cool to room temperature.

When cool, cap the jugs tightly and transport. For extra safety, I'd put the jugs in a plastic tote -- one with solid bottom and sides -- to keep the jugs from sliding around in the car and to contain any spills, just in case.

Many people make a 50% NaOH solution, but in your case I'd make the masterbatch solution to the correct % lye you want to use in the soap.

I use this rubbermaid pitcher for my masterbatched lye.
Please do not use Mason jars or glass containers. The lye will etch the glass and can cause breakage.
Several folks on here use well-cleaned liquid laundry detergent bottles.
Hope this helps some. I'm sure others with more info will be along shortly


ETA: See, I told you ^^^ DeeAnna types faster than I do!

For very short term storage, glass technically would work. But the consequences of breaking one glass jar of concentrated NaOH solution ... I don't want to think about it. Bad enough in the lab where people are trained for chemical safety, but nasty stuff in a room of "civilians". Please don't use glass ... you'll make me feel better.

I saw a bunch of wide-mouthed gallon jugs with a 5 on the bottom with lids at the Dollar Store for $1.

Another option might be to get a 5 gal. plastic bucket with a lid. If you have a Firehouse Subs near you, you can get their buckets for $2. get the lids that have 4 petals - they are easier to open and close. I wouldn't fill it up with lye water b/c that would be heavy. but 2 or 2.5 gallons would be workable.

Another option would be to use ice as part of your water. This can be tricky b/c the lye may not dissolve as easily. Maybe 10% or less. Mix the lye and water. Make sure the lye is thoroughly dissolved. Then add the ice cubes.

Another option would be an ice water batch. Mix lye and water. Again, make sure lye is thoroughly dissolved. Put the lye pitcher in a tub or sink with icy water.

I master bath 50/50 a gallon at a time in 2 gallon #2 HDPE buckets, with some ice water in the sink and leave them overnight to cool. I always put my buckets in the sink in case they decide to leak. they will get very hot, which is why I give them an ice bath. The next morning I carefully pour my solution, using a funnel, into well cleaned dish soap gallon bottles. Again this is done in the sink in case of a spill. Rubbemaid pitchers also work well for master batching smaller amounts and make it easier to pour into bottles.

Thank you all! So can I say "cooleo" to what I understand you as saying - that I can use the distilled water bottles (HDPE) to put the lye water in? I can just pour, measure, stir, dissolve, then pour the lye water back into the water bottle it came from?!?! Wow. That would be so easy. It won't eat through? And then so easy to pour! It would be ideal for me to mix the lye water Friday and then put it back in the water jugs. That way it will be room temp Saturday morning. Really? I can? Woot woot! Or as my little Princess Buttercup would say "Hooray!" Correct me if I am wrong... *hugs*

Except the caps are not secure on distilled water bottles. I have gallon dish soap bottles that have child proof caps

If you have jugs for distilled water that are like plastic milk jugs with a screw-on cap, that will work. I think Carolyn's concern is the distilled water jugs that come with snap on caps. Those are less secure in case of trouble -- and that's what you have to plan for, especially since you're transporting the lye.

DeeAnna said:

If you have jugs for distilled water that are like plastic milk jugs with a screw-on cap, that will work. I think Carolyn's concern is the distilled water jugs that come with snap on caps. Those are less secure in case of trouble -- and that's what you have to plan for, especially since you're transporting the lye.

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Exactly what I was talking about, sorry I did not clarify. I have never had or seen distilled water in any bottles with screw on caps but could just be where I live.

We get both kinds of caps on distilled water jugs here in Iowa. Maybe it's regional brands vs. national?

Anyway, I wanted to say your advice about the snap on caps is a good idea, Carolyn -- thanks for bringing it up!

Check the bottom of the container. If there is a 2 or a 5 inside the arrows, that type of plastic can hold lye water.

If you want to re use the jugs, I would pour the lye water into the jug (gloves and goggles!) and let it cool. Once it is cool, put on the cap and secure the cap with tape. Not Scotch tape - masking tape or duct tape.

Write LYE in BIG letters on all sides of the jug!

DeeAnna said:

Anything made from these plastics -- PP (polypropylene), HDPE (high density polyethlyene), or LDPE (low density polyethylene).

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From my notes I have the following info:

Melting points:
PP #5: 130°C,
HDPE #2: 90°C,
LDPE #4: 65°C,
PVC #3: 60°C

I also have observed that when I dissolve NaOH in pellet form the temperature of the lye solution is reaching 90-95°C while NaOH is in flakes form the solution reaches around 100°C.

So the #4 and #3 plastics are not capable of handling the temperature of the fresh NaOH solution except if are using ice instead of water and we control the maximum temperature that the reaction will reach with a cold bath also.

HDPE #4 also seems to me a plastic that has marginal temperature that can handle fresh NaOH solution with safety.

So I guess (and I am also only using) PP #5 plastic is the only one that is 100% safe for such job.

Am I somewhere wrong?

Please double check your sources. I am certain none of these plastics melts below the boiling point of water (below 100 C, 212 F). A quick check shows melt point of LDPE at 105 C (220 F) and I'm certain HDPE is higher yet.

As I wrote earlier, PP, HDPE and LDPE are all good choices for storing lye solution.

"...LDPE is unreactive at room temperatures except by strong oxidizing agents. It can withstand temperatures of 80 °C [175 F] continuously and 95 °C [203 F] for a short time...." *

"...HDPE bottles offer stronger tensile strength than LDPE containers, are harder and more opaque, and can withstand somewhat higher temperatures: 120°C (248°F) for short periods, 110°C (230°F) for longer periods...." *

My lye solution tops out at more like 75-85 C (170-180 F) when I mix it. And what's also important, I am not holding the solution at that temperature for storage -- it's only at that max temperature for a very short time. LDPE, HDPE, and PP can all be used for mixing and storing lye solution, as long as the container is also sufficiently sturdy and has a secure cap. I do think many LDPE containers found in every day life are rather on the lighter side -- a person would want to pick the most sturdy LDPE container available.

I didn't mention PVC as a suitable plastic for lye storage and still won't. It's not on my list for a number of good reasons, including temperature and durability concerns.

* http://www.calpaclab.com
Also note "...Sodium hydroxide 50% -- LDPE / HDPE at 20 C° - 50 C° show little or no damage after 30 days...." from http://www.calpaclab.com/chemical-compatibility-charts/

I agree with that - as a quick test if a container is suitable for mixing lye for me is to pour boiling water in to it. Many containers with those ratings are very happy with it

Thank you very much DeeAnna I will update my notes.

I don't like mixing my lye solution in a #2 because the plastic softens up. It does not melt, but it is difficult to have it hold its shape when trying to stir. #5 seems to not deform as badly.

#2 between the arrows. snap on caps. not worried about the heat (i will cool it before i pour it back in) as much as the lye IN the water. i mean, tv says lye will dissolve bodies, and afterall, everything on tv is true, right? ;-)
since family is spread out across the U.S. i have become quite skilled at taping things shut for transport. thank you for the reminder on that. i will label and tape the lye bottles. all of your comments are so helpful! i truly appreciate! now i am going to keep my eyes open for screw-on lids for water. i have not seen those (for gallon bottles). hugs to all! (Now to line every single mold I and my DIL have. bleh.)

Susie said:

I don't like mixing my lye solution in a #2 because the plastic softens up. It does not melt, but it is difficult to have it hold its shape when trying to stir. #5 seems to not deform as badly.

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I agree about the #2 HDPE, especially when I mix 1.5 gallons at a time. It will get very hot so it is in the sink with a water/ice bath

P.S. - Kroeger brand water has screw-on caps.