measuring accuracy

[Oregon Goat Momma]

I finally made my first batch of soap. Ran everything through the Brambleberry Lye calculator. The amounts of ingredients I needed came out in the hundredths place: 8.96 ounces of coconut oil, 4.05 oz lye, 9.06 oz water, for example. I was really surprised to learn that my digital scale (that says it can measure as little as .05 ounces) only gives readouts to the tenths place.

How precise do my measurements need to be when making soap? I went ahead and rounded everything, assuming the soap would be safe since I had calculated a 5% superfat.

If I need to get a new scale, I'd appreciate a recommendation. Thanks!

 

[KiwiMoose]

When you re starting out you need to be pretty accurate. Once you are experienced you get a better feel for how much more 'flexi' you can be. As little as 5 grams extra of lye for example can make the difference between 5% superfat and 0% superfat in a small 1 - 2 pound batch.
I can't help with ounces sorry - those measurements are very confusing to me.. I do know that a lot of Americans soap in metric even though they don't use metric - simply because it's more accurate?

 

[Zany_in_CO]

ingredients I needed came out in the hundredths place: 8.96 ounces of coconut oil, 4.05 oz lye, 9.06 oz water, for example.

I like working with whole numbers so I tend to round up or down when dealing with hundredths.
8.96 to 9 oz
4.05 to 4 oz
9.06 to 9.1 oz.
... then recalculate the lye amount needed. Usually it stays the same.

 

[paradisi]

No. It's just simpler for conversion to percentage. Accuracy is dependent on the precision of the scale, not the units used. .. and the carefulness of the operator.

When you re starting out you need to be pretty accurate. Once you are experienced you get a better feel for how much more 'flexi' you can be. As little as 5 grams extra of lye for example can make the difference between 5% superfat and 0% superfat in a small 1 - 2 pound batch.
I can't help with ounces sorry - those measurements are very confusing to me.. I do know that a lot of Americans soap in metric even though they don't use metric - simply because it's more accurate?

 

[Blufuz]

I read a trick that you can switch your scale to grams, and it will have more precision than in ounces, but I never tried.

The precision you need depends on the size of your batches. To ball-park how much that is, I recommend using a slightly more advanced lye calculator (even just The sage), then it tells you the different amount of lye needed to reach different amounts of superfat. you need to have the measurement precision that lets you safely avoid going under 0% superfat given the superfat you plan on doing. So if 0% superfat is 1.00 oz of lye, and 5% is 1.05, then you should have at least .01 oz precision but I strongly recommend .001 oz. If 5% is instead 1.5 oz, then you can have 0.1 oz precision, but again better one more decimal lower. If you are trying for 0% superfat, then you definitely need the precision that is 1 decimal spot less than the difference in lye to 1% superfat (0%: 1.00; 1%: 1.01; precision needed: 0.001)

 

[Zany_in_CO]

It's just simpler for conversion to percentage.

That's certainly simpler. BUT. You can still end up with hundredths of an oz.

you can switch your scale to grams, and it will have more precision than in ounces,

TRUE. That's what I do for small batches where accuracy becomes more important.

but I never tried.

Look for the MODE button on your scale. That's what I use to switch back and forth from ounces, to grams, kilograms, or pounds. It's a very handy feature for soaping as well as mailing packages.

I recommend using a slightly more advanced lye calculator

FYI: Soapmaking Friend is certainly the most "advanced", but SoapCalc is more universally recognized by soapmakers here, on YouTube, on blogs and web sites, etc. Once you get used to it, there are all kinds of ways to manipulate it to use it for other things.

For example, It's great for side-by-side comparison when you want to sub one FA for another: See screenshot

100% Coconut Oil entered in the right column.
Tick down the list of oils one by one to compare each one.
They (i.e., Castor) show up in the left column.
That's how I learned that lard was a good sub for shea butter -- and vice versa.

I use it for lotion making. It doesn't matter what FAs you enter as long as it's the same number of items in the recipe. I enter the amount of grams or ounces for each item. Then I convert the recipe to %s. Once I have the % of each item, I enter the size batch I want to make, i.e. 100g or 1000g, to get the amounts I need.

It's a good thing.

 

[Zing]

Congrats on your first soap!! Can we see proof?
Big ditto on switching to grams. Because they are smaller units, they're more precise. I am a hobbyist and make small batches at a time.

 

[Zany_in_CO]

I am a hobbyist and make small batches at a time.

Me too. I prefer grams for small batches, soap or leave-on products. 100 grams = 100% So much easier to scale up from there with the metric system.

 

[Johnez]

Me too. I prefer grams for small batches, soap or leave-on products. 100 grams = 100% So much easier to scale up from there with the metric system.

This! I do this for shave soap, I love how percent=grams on 100 gram batches. It's the only way I can keep this as a hobby and not have half my living quarters filled with tubs of soap lol.

 

[lucycat]

Even though the precision from the scale will be the same in oz or grams My precision will be better in grams. The whole number grams are easier to read on my scale and less chance of me making a mistake.

Scaling up/down a recipe is easier with metric measurements, and I do it often in a spreadsheet to adjust for embeds and shreds. The same reasons, whole number grams rather than having to work with fractions of ounces.

My vet uses a scale in pound/ounces. The assistants who weigh my cats sometimes say 9.7 for 9 pounds 7 ounces and others for 9 pounds and 7/10 of a pound. Maybe not important for my cat's weight but important for soapmaking that you know what the readout of your scale means if working with fractions of pounds/ounces. If fractions aren't your strength grams will lessen potential measuring misstakes.

 

[Oregon Goat Momma]

Congrats on your first soap!! Can we see proof?
Big ditto on switching to grams. Because they are smaller units, they're more precise. I am a hobbyist and make small batches at a time.

Thanks!
We are still awaiting the big day when we can test these out! These are the prettiest bars from the tiny batches I made. The recipe said to unmold and cut at 24 hours, but I think that was too early, as the first bars I tried to cut were a mess. I smooshed those together and made a big soap ball - the rest I waited to cut until another two days had gone by. I sprayed the top of the soap with 99% alcohol to prevent soda ash - was I supposed to do the cut bars, too? I am seeing a lot of white residue, especially on the sides and bottom of the bars.

 

[Zany_in_CO]

We are still awaiting the big day when we can test these out!

After about a week or two, I keep a small soap sample at my kitchen sink to test drive on a daily basis to see how it performs. You could do that by cutting your "big soap ball" in half.

TIP: I've never experienced soda ash, but I sometimes wash all the bars in warm salt water in the sink to smooth any imperfections. It seems to harden the bars a little too.
The soapy water in the sink is wonderful for washing up dishes.

 

[Oregon Goat Momma]

After about a week or two, I keep a small soap sample at my kitchen sink to test drive on a daily basis to see how it performs. You could do that by cutting your "big soap ball" in half.

TIP: I've never experienced soda ash, but I sometimes wash all the bars in warm salt water in the sink to smooth any imperfections. It seems to harden the bars a little too.
The soapy water in the sink is wonderful for washing up dishes.

I did it! And I love that ugly soap ball!

Maybe a little off-topic here, but I found and was reading your Beginner's Learn to Soap Online post, and was looking through all the recipes at the Miller's Homemade Soap page. I was reading the notes about oils at whatever temp, and lye solution at whatever temp. This raised new questions for me. I made my second ever soap batch on Saturday, and I decided to try my hand at goat milk soap. Milked my doe. Weighed the milk. Froze it in ice cube trays. Added the frozen cubes to the lye, and proceeded. My lye solution and oils were more like 75 degrees when I combined them - not anywhere near the 110-140 I am seeing in the recipes on that page. Everything turned out beautifully (I think). Is there anything soap-safety wise I need to be worried about with these bars? Thanks!