What do I need to know about lye before making cold processed soap?

[Elysium82]

Hey guys,

I am totally new to soap making and I have seen a few cool videos on YT - like this: that seemed simple enough, but there are 2 things I do not understand about lye.

1, Are there different types of lye? If yes, which one is the least damaging to the skin? Or does lye get totally neutralised after saponification? Or is there a totally natural way to substitute lye?

2, How do I know how much lye to put? Well, this is a bit of a silly question, but I have seen a few people talk about superfats and whatnots (things I still dont understand, but I am pretty sure I'll get there). So, it makes me wonder how one calculates the amount of lye needed. I guess it highly depends on the type of oil too.
Can I make, say, cold processed soap of 100% virgin oil and add X grs of lye to 100 ml of virgin oil and just simply double the amount (2*X amount of lye) to 200 ml of virgin olive oil if I want a bigger batch next time? Is it a linear increment?

Thank you in advance.

 

[Catscankim]

I am pretty new to soaping, so i dont have advice, but welcome to the craft! I am finding it totally addictive

 

[GemstonePony]

I'm unimpressed with that tutorial as it missed a lot of things in its haste to get to the recipe:
a) the only substances that can interact with lye safely are polypropylene plastic, stainless steel, and silicone. It will eat everything- and I do mean EVERYTHING- else. You can use high density polyethylene with caution as it may melt, and you can use wood as a disposable one-time-use tool as the lye will slowly eat the wood causing it to shed splinters.
b) It will etch glass, weakening it until it abruptly shatters, so I'm unimpressed that he's using it at all.

On YouTube, Katie Carson at Royalty Soaps did a better tutorial, and Anne-Marie from Brambleberry made the same glass mistake but talks a bit more about safety.

On to your questions:
1a. There are different types of lye, Sodium Hydroxide for bar soap and Potassium Hydroxide for liquid soap.
1b. They will both burn you and eat things, it's their job.
1c. If calculated and measured correctly, the lye will be used up turning the fatty acids in the oils into alkali components, which cure to become alkali salts aka the soap we all know and love. You should continue to handle it with gloves for the first few days after it cures, since it may take that long to saponify.
1d. Without being fed to a strong alkali, oils and butters remain just oils and butters. You could use synthetic detergents to clean instead, but then it is no longer soap. We have a synthetic detergent (syndet for short) forum as well, if you want to go that route.

2a. Soap calculaters are what most of us use to figure out lye. This forum has one in the side bar, Brambleberry. com has one, and I know there's another really good one out there but I forget where- most soap websites have one.
You just put in the type of oil and how much, tell it how much of a superfat you want, tell it if you're making a bar, liquid, or mix, and it tells you how much lye you need. It also usually gives you a clue as to the potential properties of the soap, so I almost play with the Soapcalc more than I actually make soap, since it costs nothing to experiment there.
2b. yes, scaling is linear, you will need double the lye for 200grams of an oil as you would for 100 grams of the same oil. HOWEVER, different oils neutralize different amounts of lye, so any changes to the recipe should be run through the soap calc.

Slightly off topic, but if you're looking at a100% Olive oil soap, Zany has a Castile recipe in the beginners section, and it is recommend to do a zero superfat so it doesn't get as gooey when you're using it.

 

[Elysium82]

@GemstonePony

Thank you. Much obliged.


Do you happen to know this calculator? It seems to be decent.

 

[Elizevt]

Hi there @Elysium82 , Welcome to the fold.
I'm also rather new here. But check out the beginner's soapmaking section. there is a wealth of information here. I'll add a link for you.
Beginner's Learn to Soap Online

https://www.lovinsoap.com/2016/01/lye-in-soapmaking/
Enjoy your soap making journey!

 

[Elysium82]

Hi there @Elysium82 , Welcome to the fold.
I'm also rather new here. But check out the beginner's soapmaking section. there is a wealth of information here. I'll add a link for you.
Beginner's Learn to Soap Online

https://www.lovinsoap.com/2016/01/lye-in-soapmaking/
Enjoy your soap making journey!

Perfect. I'll head there and check it out. Thanks.

 

[GemstonePony]

@GemstonePony

Thank you. Much obliged.


Do you happen to know this calculator? It seems to be decent.

It looks like it will give you the necessary information for oils. It doesn't look like it has additives or a notes section, so it wouldn't be my preference, but it'll do fine for simple batches.

 

[artemis]

I agree with the suggestion to check out Royalty Soap's recent beginners series. It was simple and straight forward.

 

[AliOop]

Welcome! Regarding a "natural" substitute for lye - no. It takes lye + oil to make soap. To determine how much lye you need for any specific combination of oils, use a lye calculator. I started with Soapcalc, but my favorite is soapmakingfriend.com.

One thing to clarify is that one doesn't literally "add lye to oils." You must dissolve the lye first in a liquid such as distilled water, aloe vera juice, goat milk, etc. As a beginner, you will want to work first with distilled water. Other liquids mean additional adjustments to your recipe, which can come later after you are familiar with the basics. One must always have at least an equal amount in weight of water to lye, but most soapers use quite a bit more water than that so their recipe is more fluid.

 

[Jillyb]

Looks like your questions have been answered above. Im sure like most of us you'll learn alot by reading here.
I look forward to seeing your future creations
Welcome to the group.

 

[TheGecko]

1, Are there different types of lye? If yes, which one is the least damaging to the skin? Or does lye get totally neutralised after saponification? Or is there a totally natural way to substitute lye?

Yes, there is Sodium Hydroxide and Potassium Hydroxide. There is also potassium carbonate aka potash. ALL can be damaging to the skin if mixed with a liquid and applied directly to the skin...they are caustic and will burn. But through the magic (science) of mixing these chemicals with oils/butters in a process called 'saponification', they are neutralized and turn into soap.

2, How do I know how much lye to put? Well, this is a bit of a silly question, but I have seen a few people talk about superfats and whatnots (things I still dont understand, but I am pretty sure I'll get there). So, it makes me wonder how one calculates the amount of lye needed. I guess it highly depends on the type of oil too.

Each oil and butter has a SAP (saponification) value; the amount of lye needed to turn said oil or butter into soap. Prior to lye calculators, you had to do the calculations by hand. As an example, it's takes 0.135 ounces of lye to saponify 1 oz of Olive Oil, 0.137 for Coconut Oil and 0.141 for Palm Oil. To make 16 oz batch of soap with equal amounts you would then multiply each weight by the SAP then add:

5.44 x 0.135 = 0.7344
5.28 x 0.137 = 0.72336
5.28 x 0.141 = 0.74448
---------
2.20256

So you would need 2.2 oz of Lye. The amount of liquid needed can very, but can never be less than the amount of your lye.

Superfat refers to the total amount of oils/butters left unsaponified.

Can I make, say, cold processed soap of 100% virgin oil and add X grs of lye to 100 ml of virgin oil and just simply double the amount (2*X amount of lye) to 200 ml of virgin olive oil if I want a bigger batch next time? Is it a linear increment?

Yes, but soap making is done by weight, NOT volume because not all oils and butters have the same density. Think of 1 lb of gold and 1 lb of feathers...same weight, completely different volume.