Lye Storage

[The Efficacious Gentleman]

Lo all

So, to all those who master batch your lye, some questions -

Obviously liquid containers are most often in volume which is annoying as solution will be mixed by weight. So first question: How much 50% solution (by weight) is needed per litre?

Next question - what does lye solution do to plastic over the long term? I'm thinking of a larger plastic container with a spigot, but wonder about degradation of the tap parts. What are your thoughts, ladies and gents?

 

[IrishLass]

Hopefully those who use a container with a spigot will chime in soon since I'm no help there. I've never used the kind of bottle with a spigot on it for my solution. When I make mine, I use a reclaimed laundry detergent bottle made of heavy-duty HDPE #2. Specifically this one: http://www.amazon.com/dp/B001KYQI0Q/?tag=skimlinks_replacement-20 (now y'all know what I wash my clothes with, lol). I like it for my solution because it has a spill-proof spout underneath that green cap so that any over-spill drains back into the bottle instead dripping down on the outside.

I've had no issues at all storing my 50% solution in it. Both the bottle and the lye solution keep quite nicely for me for at least over a year (I conducted an experiment to find out). They most likely would have lasted just fine even longer than that, but I wanted to make soap with it and could wait no longer! lol

I wish I could tell you exactly how much solution will fill my 4.43L bottle, but that is one thing I have not bothered to work out with precision yet. I just make enough solution at a time to make seven 2.5lb batches of soap, which fills my bottle up about half-way or so with solution. I could make more than that, of course, but my mixing pitcher is not big enough (I mix in PP #5 and store in HDPE).

IrishLass

 

[dixiedragon]

I am very curious about master batching. I get masterbatching oils - but does master batching lye water really save that much time? If you generally make the same size batch over and over, I would think it would be easier to measure out the amount of lye you use and store it in small containers.

 

[DeeAnna]

The specific gravity of a 50% NaOH and water solution at 20 C (68 deg F) will be 1.52, give or take a tiny bit. It becomes less dense as the temperature goes up.

So if 1 L of water weighs 1000 g at 20 C, then 1 L of 50% NaOH will weigh 1.52 X 1000 g = 1520 g.

 

[autumngirl27]

I make "small" master batches of my lye solution (and it has really been a game-changer!). I use wide-mouth 2000 mL bottles, and I can fit about 900 grams of NaOH and 900 grams of H2O in each bottle with a comfortable amount of room to spare.

I've never made enough lye solution to use a container that has a spigot, but in "Scientific Soapmaking," Kevin Dunn recommends polypropylene plastic for mixing and storing lye, as it is resistant to high temperatures. So I presume that so long as your larger container and the spigot are polypropylene, the plastic should hold up over time.

 

[The Efficacious Gentleman]

Good point! I was in the garden centre yesterday and saw some that looked good, except that the tap was at an angle that might cause issues with pouring.

 

[DeeAnna]

I hadn't quite tumbled to the fact that y'all are looking at containers with spigots until I read The Gent's latest post.

I'll offer a caution as an engineer who used to deal with dangerous chemicals in tanks and such. You need to make sure the gasket and o-ring materials in the spigot part are also suitable for NaOH. Some sealing materials are a rubber or a synthetic rubber. While that might be great for water or iced tea, it might not be the best for lye.

You can get away with marginal gaskets if they aren't directly and continuously exposed to the liquid. An example might be a cap on top of a lye storage container. But once the sealing material is exposed full time to the lye, as it would be for a valve on the bottom of a tank, then it's very wise to pay close attention to materials of construction.

 

[Saponista]

I was looking at these as I used to use them at work for acid wash storage. The tap is made of polypropylene as well as the bottle so would cope with lye exposure. They are more expensive than something from a garden centre but I would have more confidence in their performance.

http://www.camlab.co.uk/autoclavable-aspirator-bottles-polypropylene-p14291.aspx

From what I remember (a few years since I have used one) they don't have an o-ring or gasket, the tap is just a screw thread that unwinds to release the liquid so there would be no issues as long as it is definitely made from polypropylene.

 

[IrishLass]

I am very curious about master batching. I get masterbatching oils - but does master batching lye water really save that much time? If you generally make the same size batch over and over, I would think it would be easier to measure out the amount of lye you use and store it in small containers.

I find that master-batching saves me the time, and (more importantly) the hassle of having to make my solution fresh each time that I feel like soaping, because when I make my solution, it's an event. lol I utilize extra layers of protection, I make sure my lye-mixing space is clear of other people who might otherwise complain that they need to use that space the same time I want to mix my solution, and they don't want to inadvertently breathe in any fumes, etc... Then I have to wait for the solution to cool to the temp at which I like to soap. etc....

When I first started soaping, I was so excited and in love with soaping that such things didn't bother me so much, but over time they've become nagging annoyances to me, especially if I'm pressed for time. It's so much easier for me to mix up a big batch of solution at one time and then soap several batches at my leisure.

Although I mostly soap 2.5 lb. batches with a 33% lye solution, I do make other batches that are smaller or bigger than that and/or that might need more water or less water than that. Working from a 50% solution is so nice because it allows me to be able to do all of that with ease.

IrishLass

 

[houseofwool]

Today I picked up an empty laundry detergent bottle that has a spigot. My intention is to keep the bottle stored on end so the tap is at the top. That way if it springs a leak, it won't be disastrous.

 

[DeeAnna]

Saponista and House of Wool -- You both have found some very good solutions - nice thinking!

 

[Dorymae]

I am very curious about master batching. I get masterbatching oils - but does master batching lye water really save that much time? If you generally make the same size batch over and over, I would think it would be easier to measure out the amount of lye you use and store it in small containers.

It saves a lot of time if you soap cold. It saves some time if you soap warm. I have just begun master batching lye and I wonder now why I took so long to do this. I used to wait at least 1/2 hour for lye to cool. I already master batch oils so there is no waiting there.

Now mixing a batch of a favorite soap is very quick and I can make soap in a fraction of the time. I appreciate it very much right now because having just moved, I am facing relabeling all my products. It is not my favorite job and I've been procrastinating.

 

[The Efficacious Gentleman]

Today I picked up an empty laundry detergent bottle that has a spigot. My intention is to keep the bottle stored on end so the tap is at the top. That way if it springs a leak, it won't be disastrous.

That is a very good idea indeed. As it turns out, these containers might well be the wrong type of plastic. But I do like the idea

 

[ngian]

From the first time I started soaping (2 months ago) I made a 50% LYE solution as I have read that it is very easy to make new soap for the reasons you all probably know and IrishLass has already made an extensive explanation in this thread.

I' m using a thick PP bottle (holds up to 1000ml and costs 1Euro) and although it hasn't any triangle symbol underneath, the soap-cosmetics supplies shop that I bought it from, has ensured me that it is safe to use with chemicals and high temperatures.

As far as how much ml of 50% LYE can hold every container, I photographed my latest production so as to have it for future reference.

I' m using pure NaOH that costs 10E / kg

which is in a form of tears:

and below you can see the results after 1hour of stirring:

I used my remaining 487,9gr of NaOH along with 487,9gr/ml distilled water, and the final 50% LYE was around 690ml.

So this also helps me in computing the mold size that each recipe will occupy in ml and when a recipe needs 100gr of NaOH that is around 40ml in volume.

My only remark is that I have seen white crystals inside the top of the screwing lid and this is might be dehydrated LYE. This is also visible at the latest photo, inside the wall of the "stirring bottle" just above the LYE level.

Nikos

 

[DeeAnna]

Your numbers are close to the 1.52 specific gravity of 50% NaOH solution as published in the chemical literature:

975.8 g lye solution / 690 mL approximate volume = 1.41 specific gravity

The slight difference between your example and the published value is probably due to error in measuring the volume of the finished solution. It's close enough.