First Salt Bar- Volume Questions

I am thinking of attempting my first salt bar recipe, and I'm having some difficulty wrapping my head around how to calculate the volume needed.

EDIT: Whoops! Didn't mean to post that- I'm not done yet!

I am planning on doing a 90% CO, 10% butter recipe, with salt at 80% of oils.

I have a cavity mold, so I can really make whatever amount and make it work, but is there a formula for determining how much oils you need? Is there a 1:1 relationship between the volume of soap batter and salts?

Also, what lye concentration is typically used?

Thanks!

The last time I did an 80% salt soap / 20% SF I just used the default water setting (2.7404:1 water to lye ratio or water as % of oil weight = 38%), largely because I like the quick gelling and this is a fast moving soap.

I'm so lazy that I don't calculate the overage and just put out extra containers / molds to fill. I use the same recipe so often that I just know to have more cavity molds about for after I fill my tall and skinny mold, but I've never quantified it - just thought "hey free soap!".

I do the same thing as Seawolfe, I like being able to have mini bars to hand out as samples or gifts.

I already tried to say this once, but the internet ate my post!

First, I am NOT a math person, but here's my thinking: if you are planning to add 80% of your oil weight in salt, wouldn't you just reduce your starting amout of oils by 80%? So, if your original batch weight is 100 units, then the salt weiht would be 80 units. The new oil weight would be 20 units and the salt weight would remain 80 units? The final total weight would still be 100 units, right?

My head just about blew a gasket when trying to figure out how much extra volume the salt might take up in my salt bar, because it is not a 1:1 volume relationship between the salt and oil weights.

RE: a mathematical formula: I'm sure there is a mathematical formula to figure such things out, but the tricky thing is that it will end up being a different formula for each person depending on their recipe, i,e., depending upon how much salt per oil is used, how much water is used, and possibly even how big the salt grains are! The easiest thing to do is just have an extra mold cavity or 2 on hand to pour the excess into and enjoy your extra soap. If you want to come up with a mathematical formula for your next salt bar batch (provided that you will be using the same ratios of salt, oil and water), just take note of how much leftover batter you end up with and calculate from there.

RE: lye concentrtation. I use a 31% lye concentration with mine, but I use 25% salt ppo. Back in the days when I used to use 100% salt ppo, I used a 28% lye concentration (i.e., full water). I found that the more salt I added, the more water was needed to be able to make cutting a less crumbly affair for me. Since you are using cavity molds, though, it might not make so much of a difference.


IrishLass

I times my normal batch size by 90%. This is a recipe using 100% salt so maybe it is not much help

artemis said:

I already tried to say this once, but the internet ate my post!

First, I am NOT a math person, but here's my thinking: if you are planning to add 80% of your oil weight in salt, wouldn't you just reduce your starting amout of oils by 80%? So, if your original batch weight is 100 units, then the salt weiht would be 80 units. The new oil weight would be 20 units and the salt weight would remain 80 units? The final total weight would still be 100 units, right?

Click to expand...

This was my original thought too...but the weights would be the same, not necessary the volume (I think ?). Since this is my first salt bar, I wasn't sure if this was a good way to estimate how much batter you'd eventually end-up with or if it might end up being way more or way less than expected.

Cellador said:

This was my original thought too...but the weights would be the same, not necessary the volume (I think ?). .

Click to expand...

Correct- the volume or actual space the salt takes up will be different in spite of weighing the same as the oil.


IrishLass

The volume is really marginally different. My usual batch size is good in my 4 moulds, and with 86% salt it hardly made a difference at all. Maybe filled them a little bit more, but we aren't even talking about a 25% volume increase.

If anything, the .9 conversion to original oil weight would be a good option