Can a batch be "too small"

Newbie here, asking questions. Since I don't want to waste product on soaps I won't like or make again and I'm still experimenting, I was thinking of making tiny batches. I have some old pvc pipe laying around, 2" in diameter and I was thinking about making tiny batches with about 100 grams of oil.

I'd get about 6 little discs of soap from a mold. Small enough to sample and mail to friends and family but not a waste if they are horrible.

Can making a batch of soap this small cause recipe problems or measurement issues? Should I stick with the larger loaf batches?

Smaller batches are harder to weight out correctly. Most people recommend 1lb as the smallest but I have done 8 oz batches before. I always superfat at 8% so I'm not too worried about inaccurate weighed lye. I don't think I would do a 100 gram batch, thats really small, not even the size of a standard bar.

I don't see how making a 100g batch is chemically different than a 1kg batch to be honest. Weighing is a good point though -

Just did a quick SoapCalc on 100g Olive Oil and it's 12.87g lye at 5% SF (superfat) - not too hard to measure out if you round down for safety. The hardest thing to measure would be the scent(s) if any - you're looking at putting in around 3 grams of scent. One scent isn't too bad, but mixing then becomes an issue as I know you have a scale that only works in whole grams (I'm such a stalker!).

One thing to also consider is how to mix. I have a nice bucket for doing 1kg batches, but wanted something to do 500g ones. I knew my bucket would be too big to get enough depth to properly mix with the old stick blender. I then searched A LOT to find a large enough container that was the right shape (not too wide but tall) to allow me to have enough batter depth for a good old mix.

For measuring scent, use plastic disposable pipettes--they come in 1mL and 3mL sizes that I know of. Most EOs are not the same density as water, meaning 1mL is not quite a gram, but it's close enough. If your scent calculation is in decimals, remember that 1mL is supposed to be 20 drops.

note--some EOs will dissolve some plastics, so if you use citrus EOs rinse the pipette with alcohol immediately and then see how it reacts.

I also have some glass syringes and stainless steel needles

MzMolly65 said:

Newbie here, asking questions. Since I don't want to waste product on soaps I won't like or make again and I'm still experimenting, I was thinking of making tiny batches. I have some old pvc pipe laying around, 2" in diameter and I was thinking about making tiny batches with about 100 grams of oil.

I'd get about 6 little discs of soap from a mold. Small enough to sample and mail to friends and family but not a waste if they are horrible.

Can making a batch of soap this small cause recipe problems or measurement issues? Should I stick with the larger loaf batches?

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If you are confident in your wieghts it's not a problem. The supper small amount is easy too since you can shake mix in a jar. The book "Scientific Soap making" suggests this method for making single bar batches. If you are doing more than one you can mix up your your lye to have a stock lye source 1:1 NaOH to water and mix up from there if you like. You simply shake the lidded jar until the batter starts to stick to the sides and mold. Bigety-Bang!

Chemically its the same but scales are more likely to be inaccurate at small amounts.

Others are correct that you have to be ultra precise in measuring, but if scale is accurate and weighs in grams, I think you'd be ok. Just round down when you measure your lye and up when you measure your oils.

Personally, I think making a 100 gram batch is a lot of work for not very much payoff. I like making 2 lb. batches because they don't use a ton of oil and I still get seven decent sized bars.

eyeroll said:

Others are correct that you have to be ultra precise in measuring, but if scale is accurate and weighs in grams, I think you'd be ok. Just round down when you measure your lye and up when you measure your oils.

Personally, I think making a 100 gram batch is a lot of work for not very much payoff. I like making 2 lb. batches because they don't use a ton of oil and I still get seven decent sized bars.

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Totally, I've also never made a soap that was "horrible", boring at worst. Friends and family get so excited about hand made soaps they get excited of soaps I personally feel pretty "pfff" about.

Like said its find as long as you have an accurate and precise enough scale.

You can use disposable pipettes for EOs. All EOs will eventually dissolve plastic, thats one sign when looking for quality EOs is to stay away from plastic bottles or plastic droppers inside the bottle. It could be that its a low quality EO, and with a high enough quality EO the plastic will eventually be dissolving and contaminating your oil.

TKB trading has a scale called the "itty bitty scale" which is cheap (10 bucks or so) which measures to the 100th of a gram. Works like a charm for small measurements.

judymoody said:

TKB trading has a scale called the "itty bitty scale" which is cheap (10 bucks or so) which measures to the 100th of a gram. Works like a charm for small measurements.

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I think I saw someone using something like that (nothing like being exact, eh!) on a soaping video for the scents.

Some great advice and some good laughs reading all this. I am a mad scientist at heart so I can see myself in some of these posts .. now maybe a lab coat to go with these crazy safety goggles, and those glass syringes .. LOL!

Oh my, a rack of test tubes for additives would be hilarious.

MzMolly65 said:

Newbie here, asking questions. Since I don't want to waste product on soaps I won't like or make again and I'm still experimenting, I was thinking of making tiny batches. I have some old pvc pipe laying around, 2" in diameter and I was thinking about making tiny batches with about 100 grams of oil.

I'd get about 6 little discs of soap from a mold. Small enough to sample and mail to friends and family but not a waste if they are horrible.

Can making a batch of soap this small cause recipe problems or measurement issues? Should I stick with the larger loaf batches?

Click to expand...

Yes.

A 100g batch of soap, using soapcalc's average SAP values, has less than 1 gram margin of error between a 5% superfat and a lye heavy soap. Yes, you can get a scale that weighs in fractions of grams, but unless you are using lab grade equipment that has been calibrated very precisely and you know the exact SAP value of your oils, it is extremely difficult to be accurate and safe. All agricultural products have variations, from one region to another, last year's harvest and this year's, suppliers, etc. Soap calculators use averages only.

Even if you got a soap you liked it would be almost impossible to reproduce the results, because you wouldn't really know if you ended up with a 2% superfat or 8%. I strongly recommend no smaller than 1 pound, preferably 2lb batches.

new12soap said:

I strongly recommend no smaller than 1 pound, preferably 2lb batches.

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Thank you .. a very educational reply and much appreciated.

"...I don't see how making a 100g batch is chemically different than a 1kg batch to be honest. Weighing is a good point though..."

There are two issues that will affect small batches more than larger ones -- controlling the saponification reaction and controlling measuring error.

A 1 gram error in your lye in a 2000 gram (4 pound) batch is only .05% error. The same error in a 100 gram batch is 1% error. If you have a scale that weighs to 1 gram, you are essentially building in an error of + or - 0.5 grams in every weighing that you do. Whether your batch is large or small, it makes no difference to the scale.

Kevin Dunn (Scientific Soapmaking) makes small batches in a chemistry lab. He has access to laboratory-grade balances that can weigh to + or - 0.001 gram or better. Those balances make a difference in the measuring error that he has to deal with.

Judy's scale might be a good choice, but I would also invest in a calibrated weight to make sure the scale remains accurate. An inexpensive scale that is that precise is more likely to have troubles in the long run -- to some extent you get what you pay for when you buy a scale.

Also, high precision scales are more delicate and require more care to do accurate weighing. Just walking across the kitchen floor or natural air movement in the room is likely to make the weight vary on this type of scale and introduce unacceptable error. That is why a high accuracy lab scale kept in a closed cabinet to reduce drafts and is put on a heavy surface that is insulated from vibrations.

Dunn also CPOPs those small batches at 170 degrees F for 1 hour. A small soap batch will be slower to saponify than a bigger batch because the surface area of the smaller batch is large in proportion to the weight. This means more heat will be lost faster from the small batch than from the large, so a small batch might need added heat, where a larger batch might need no heat or need to be cooled down.

DeeAnna said:

A 1 gram error in your lye in a 2000 gram (4 pound) batch is only .05% error. The same error in a 100 gram batch is 1% error. If you have a scale that weighs to 1 gram, you are essentially building in an error of + or - 0.5 grams in every weighing that you do. Whether your batch is large or small, it makes no difference to the scale.

Kevin Dunn (Scientific Soapmaking) makes small batches in a chemistry lab. He has access to laboratory-grade balances that can weigh to + or - 0.001 gram or better. Those balances make a difference in the measuring error that he has to deal with.

Judy's scale might be a good choice, but I would also invest in a calibrated weight to make sure the scale remains accurate. An inexpensive scale that is that precise is more likely to have troubles in the long run -- to some extent you get what you pay for when you buy a scale.

Also, high precision scales are more delicate and require more care to do accurate weighing. Just walking across the kitchen floor or natural air movement in the room is likely to make the weight vary on this type of scale and introduce unacceptable error. That is why a high accuracy lab scale kept in a closed cabinet to reduce drafts and is put on a heavy surface that is insulated from vibrations.

Dunn also CPOPs those small batches at 170 degrees F for 1 hour. A small soap batch will be slower to saponify than a bigger batch because the surface area of the smaller batch is large in proportion to the weight. This means more heat will be lost faster from the small batch than from the large, so a small batch might need added heat, where a larger batch might need no heat or need to be cooled down.

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True True, Dunn also devotes allot of material to methods of proper measurement and points out that the advantage of soap makers to keep two scales for small and larger weighing.
For those who haven't read it the book is set up like a text book with labs and tests at the end of each chapter. I'd like to go through it doing the labs while I read but me and another soap maker are in a hold fight with the only copy my counties library has and with everything else I haven't found the time to give it a proper go. It's on my Amazon wish list and I plan to buy it when I stop blowing what spare cash I have on EOs and oils.