Just-soft-enough soap to cut?

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Hello, everyone!
I got a request for a block of soap that could be cut into bars as needed, rather than pre-cut. Does anyone have experience with this? Is there a way to get soap just soft enough to cut for up to a year or more, but not so soft that it dissolves extremely quickly? I’ve made a few unintentionally soft soaps, but they often flaked off chunks when using.

My requester has really hard water, so I figured it wouldn’t be great to go with a high superfat, since I think that leads to soap scum?

Are there additives that sort of do the opposite of sodium lactate? Or is it just a question of getting the right blend of oils?

Any advice would help!
 
Soft enough to cut for maybe 4-6 months, sure. I imagine there are a number of recipes that will give you that, but from personal experience, I can say soap that has a high % of lard (50-60%) can be cut for about that long although the soap gradually gets harder to cut as time goes on.

To get bar soap that can be nicely cut for up to a year, I'm doubtful. Every soap becomes firmer over time as it continues to lose moisture and continues to crystallize. Even a soap high in lard is hard to cut when it gets that old.

Kiwi's suggestion of using KOH and NaOH might be a possibility, however. I know a 100% KOH shave soap remains permanently soft, but a 5% KOH soap hardens about the same as a 100% NaOH soap. So you're looking at more than 5% KOH, but I can't tell you how much more never having looked into this idea. The tradeoff is the soap, due to being permanently softer, isn't going to last as long.
 
Kiwi's suggestion of using KOH and NaOH might be a possibility, however. I know a 100% KOH shave soap remains permanently soft, but a 5% KOH soap hardens about the same as a 100% NaOH soap. So you're looking at more than 5% KOH, but I can't tell you how much more never having looked into this idea. The tradeoff is the soap, due to being permanently softer, isn't going to last as long.

Why would you add 5% KOH if it doesn’t change the softness?

I don’t yet have KOH, but when I eventually find a supplier, I might give this a try; it’s an interesting idea
 
I got a request for a block of soap that could be cut into bars as needed, rather than pre-cut. Does anyone have experience with this?
Yes, I have. I make soap in WSP's 1501 Silicone Mold that can be cut into 7-8 bars or whatever size the customer wants. 30-33 oz. batter makes 40 oz. soap (approx) that fills the mold to the top. For the customer to make the most of shipping costs, I encourage them to buy 2 loaves at a time -- enough soap for a year or so.

I've never had a. complaint about their ability to cut the soap -- even after the normal 4-6 week cure before shipping.

I use the Default Setting on SoapCalc, i.e., full water, 5% SF and fragrance according to use-rate by the suppler, usually 0.5% for EOs; 0.85% for FOs.

Recipes that ship and cut well after cure:

Lard Soap with 10% Coconut, 85% Lard, 5% Castor
Basic Trinity of Oils with 25% Coconut, 30% Olive, 40% Shea Butter, 5% Castor
Zany's No Slime Castile (as written) with 10% Coconut, 85% Olive, 5% Castor
 
Why would you add 5% KOH if it doesn’t change the softness?

I don’t yet have KOH, but when I eventually find a supplier, I might give this a try; it’s an interesting idea
I find soap recipes high in palmitic or stearic acids will kick up lather faster if you use 95%/5% NaOH/KOH, which is how I always soap. As to your main question I cannot answer since all my soaps would be too hard to cut even before cure time is finished.
 
Yes, I have. I make soap in WSP's 1501 Silicone Mold that can be cut into 7-8 bars or whatever size the customer wants. 30-33 oz. batter makes 40 oz. soap (approx) that fills the mold to the top. For the customer to make the most of shipping costs, I encourage them to buy 2 loaves at a time -- enough soap for a year or so.

I've never had a. complaint about their ability to cut the soap -- even after the normal 4-6 week cure before shipping.
that’s a good idea, shipping the block whole and letting the customer decide the size. But I think what my friend had in mind was that she would cut each piece of soap when she needed it, so if she needed to travel somewhere she would cut a small piece, etc. But if I can’t find a long-lasting soft soap, this is what I will suggest she do 👍
 
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