Fluctuations in recipe volume

[SoapAddict415]

I'm not sure what happened here and I'm hoping that someone has a clue. I made a recipe 3 times. I was .01 over on my water amount twice (1st & 3rd batch) and 1 oil once (2nd batch). I used the same molds, 1.5 oz individuals. The first batch, I got 11 soaps but I didn't fill the molds all the way to the fill line. The second batch I got 9 soaps and 8 with the 3rd batch. I filled the 2nd & 3rd batches to the mold fill line. Each time I used 9 oz oils, 38% water, 6% SF, 8% Apricot kernel oil, 40% lard, 30% EVOO and 22% palm kernel flakes. My additives were .1 oz sodium lactate and 1 teaspoon of colloidal oats. My fo was .3 oz. I made the first batch last week and the other 2 batches were made this morning. I'm sure that not filling them all the way is why I got 11 out of the batch #1. What I can't figure out is how I ended up 1 soap short on batch #3.

 

[earlene]

Assuming this is CP, and not HP (which would be very easy to explain why), then I'd suggest starting with a scale calibration.

If you have a users manual with your scale, follow the instructions. If not here is one article with details for calibrating digital scales and other information.

https://blog.beamex.com/weighing-scale-calibration-how-to-calibrate-weighing-instruments

If you don't have weights, you can purchase some at various locations including Amazon:

https://tinyurl.com/yb5bvggp

and Walmart: https://tinyurl.com/ycntfdtq

Or Google Search for your scale make & model for how to calibrate it and you will probably find something to follow.

I'd start with scale calibration. But, first, I'd also like to suggest that even when the scale is totally accurate, user errors can occur with scales. I have noticed that sometimes I have something too close to my scale and if it touches the scale, it can give me a false reading. I have also seen grocery cashiers rest their hands too close to or on the scale in a grocery store (my husband says this is more common when the clerk is very tall because they have to bend over while weighing the produce.)

ETA: Another possibility is the accuracy of your scale. Is it a .01 accuracy or a .1 accuracy kind of scale? If it only measures to 0.1 accuracy, your tenth of ounce measurements could be potentially off by quite a bit.

 

[SoapAddict415]

Thanks Earlene! It's a .1 scale. I'll try to calibrate it. It wouldn't surprise me if that's the culprit. I've had it for years. I work with a scale at work to count small parts so I try to be mindful of not having things near the scale. The slightest breeze from a fan or even paperwork touching the scale will throw me off count.

 

[DeeAnna]

It may be less about changes in total batch volume and more about how are you cutting your bars. It is very easy to get fewer or more bars with very slight changes in the bar thickness. An increase or decrease of just 1 mm or 1/16 inch adds up to a large error over 8+ cuts.

 

[Obsidian]

@DeeAnna, I believe OP is using cavity molds. I know when I use cavity molds, if I fill them very full I will get 5 bars instead of 6 (for a 1 lb recipe).

I think the only way to know if you batches are really different is:

1. weight the batch before pouring. This will only work if you use the exact same recipe and additives.
2. use a transparent container with measurements so you can see the actual volume

 

[SoapAddict415]

It is CP and individual silicone molds. The only difference is the color and fragrance.

 

[dibbles]

Weigh all the bars together from each batch and see what the difference actually is. A little difference in how full each mold is could account for part of it. It looks like the green batch was split for two colors - that might mean a little batter left behind in two containers rather than just one. It wouldn't account for all of the difference, but could be contributing.

 

[SoapAddict415]

The green batch is 2 colors, neon green and tumeric. I'll weigh the batches after I unmold. They looked the same but maybe I did fill 1 batch a little fuller than the other.

 

[DeeAnna]

My bad. I stand corrected! Thanks for pointing that out.