I want to share that I've discussed this recipe with Kevin Dunn. I asked him for his thoughts on what is causing the lye to neutralize. I truly don't think he'll mind my sharing his part of our discussion with y'all, so here is our email conversation:
***
Hello, Dr. Dunn,
May I ask for your thoughts on a soap making problem?
There are a group of us on the Soap Making Forum (http://www.soapmakingforum.com) who are experimenting with an unusual Castile cold-process soap recipe originating in Andalusia. The recipe is basically this:
Olive oil, any given volume (the original recipe called for 6 L)
NaOH sufficient for saponification plus a -40% "super lye" excess (in other words, if 100 g of NaOH is sufficient for saponification, we would use 140 g for this recipe)
Water equal to the NaOH weight
Water equal in volume to the olive oil
Dissolve the NaOH in the first portion of water to make a 50:50 lye solution. Add the lye solution to the oil. Add the second volume of water to the batter. Stir by hand until trace; this usually takes about 60 minutes. Pour into a mold and let set.
As you would imagine, the soap is very lye heavy at first, but our experiments are showing the bars of this soap are becoming tongue neutral in about 2 weeks. I have split some of these bars and confirmed that the centers are tongue neutral as well as the exterior.
The purpose of the NaOH excess is to eliminate or reduce the gooey and slimy nature of Castile. We tentatively think a -30% to -40% super lye is critical -- less lye does not reduce the goo/slime factor.
The water excess may also have something to do with reducing the slime/goo factor, but it definitely looks like it is the key for reducing the excess lye to safe levels. For about a week after the bars are first cut, the soap is unusually damp and cold from evaporation. This evaporation is transporting NaOH solution to the surface where some of the Na+ is reacting with CO2 to form soda ash.
But my calculations suggest the formation of soda ash can only be part of the neutralization process -- there is much more excess lye than there is soda ash formation (see photos). Being an engineer, I'm not content to just accept that this neutralization just magically happens. Unfortunately, my studies are not dredging up any clues about other routes of dealing with this lye excess.
Can you suggest any ideas for me to research?
Many thanks for considering my request -- I sincerely appreciate any help you care to offer.
Regards,
DeeAnna Weed, PhD
[I also sent pics of bars from the two batches I've made plus pics of the lather for both.]
***
Hi DeeAnna,
Wow, that's a lot of water for a CP soap. I'm surprised it sets up at all. As for the lye excess, my experiments with excess lye up to about 5% also show that the soap becomes tongue neutral over a few weeks. I have supposed that CO2 from the air neutralizes the excess lye, but I have not tested this. If I were to do this I would proceed as follows:
1) Cut identical bars from the superlye batch
2) let 1 bar cure in air as usual
3) seal 1 bar in a mason jar to exclude CO2 (this bar will not dry out)
4) the last test is a little more involved--you want to exclude CO2 but allow water to evaporate. If you have access to bottled nitrogen gas you could fit up a sealed box with a slow nitrogen purge. Otherwise, place the soap in a sealed container large enough to hold an open mason jar of dry NaOH. Over time the NaOH will absorb both water and CO2, allowing the bar to dry out.
5) from week to week, test a sample of each bar of soap for neutrality. The tongue test would give you some information, but if you want to follow the process precisely, titrate each sample to determine total alkalinity, as described in my book.
Please let me know what you discover. This sounds very interesting.
I am also surprised by the lather you are getting from this soap. I wonder whether it comes from the sodium carbonate. To test this you could knead a little sodium carbonate into a "slimy" castile soap to see whether the lather quality is improved.
Kevin M. Dunn
Professor of Chemistry
Hampden-Sydney College
***
Hello, Kevin,
Thank you for your kind and thoughtful reply!
I am setting up an experiment similar to what you propose. I thought about the design of the last test (item 4 in your email). I don't have the ability to create a dry nitrogen purge and I hesitate to use NaOH as a desiccant, so I think I will use a silica gel desiccant pack instead. I was looking for the old calcium chloride desiccant I used to use in the lab, but silica gel was easier to find locally. As far as doing TA analysis, no problem. I used to work in an industrial chem lab. It's going to be weird to titrate without a buret and all the other bits of lab equipment I used to use, but I'll get used to it!
As far as the lather goes, yes, the soap is lathering well, although it seems as if there is something on the surface of the bars that is interfering with easy formation of the lather -- maybe soda ash, maybe glycerin, maybe lack of water for bubble formation? I'm not sure. At times the lather seems scant and "ropy", but then it will develop a nice froth of bubbles as in the photo I sent. I'm not too concerned about it at this point, since most of our soaps are only 3 weeks old or less, but it will be something we will continue to test as the soaps get older.
And I agree with you -- this recipe calls for a LOT of water -- the final NaOH solution concentration is roughly 15% w/w. The abundance of water makes for some tricky moments during the mixing and molding. A few of us have had problems with the emulsion failing during trace or later when the soap is in the mold, but we're finding this is related to a couple of factors. One is any extra warmth created by over-insulating the molded soap or putting the mold in a 170 F oven to CPOP.
The second factor is too much agitation. Some of us getting the most consistent results by hand stirring only, but others are doing okay by mostly hand stirring and just lightly stick blending for short periods up to heavy trace. After that, it's safest to pretty much hand stir only until it's time to pour in the mold. We do know if the emulsion does break from stick blending that it can be re-established by going back to hand stirring. That seems counter-intuitive, but I'm thinking a fragile water-in-soap emulsion is able to form with only low-energy stirring, but the high shear from stick blending is breaking down this structure and allowing some water to separate from the batter.
I re-read chapter 15 in your Scientific Soapmaking book about the alkalinity tests you did on the 11 week old soap. It sounds like what you observed is what we're seeing with this recipe -- an unexpectedly large reduction in the alkalinity with time. I would not have expected remotely as much reduction as we're seeing, but our simple zap tests and handwashing tests are showing a striking decrease in the excess alkalinity.
I will keep you informed! Thank you for your insights and suggestions -- I appreciate the help in getting unstuck in my thinking.
Regards,
DeeAnna
***
So ... I'm back ... I'm in the process of gradually setting up an experiment or series of experiments to test this soap recipe. I'm open to your suggestions and ideas on how to proceed. Although I think Kevin's suggestions are worth following, I'm sure you folks will have good ideas to consider as well. Let me know!
Oh, and if anyone has a burette or a 125 mL or 250 mL Erlenmeyer flask collecting dust in the pantry, I'd be glad to buy it.
***
Hello, Dr. Dunn,
May I ask for your thoughts on a soap making problem?
There are a group of us on the Soap Making Forum (http://www.soapmakingforum.com) who are experimenting with an unusual Castile cold-process soap recipe originating in Andalusia. The recipe is basically this:
Olive oil, any given volume (the original recipe called for 6 L)
NaOH sufficient for saponification plus a -40% "super lye" excess (in other words, if 100 g of NaOH is sufficient for saponification, we would use 140 g for this recipe)
Water equal to the NaOH weight
Water equal in volume to the olive oil
Dissolve the NaOH in the first portion of water to make a 50:50 lye solution. Add the lye solution to the oil. Add the second volume of water to the batter. Stir by hand until trace; this usually takes about 60 minutes. Pour into a mold and let set.
As you would imagine, the soap is very lye heavy at first, but our experiments are showing the bars of this soap are becoming tongue neutral in about 2 weeks. I have split some of these bars and confirmed that the centers are tongue neutral as well as the exterior.
The purpose of the NaOH excess is to eliminate or reduce the gooey and slimy nature of Castile. We tentatively think a -30% to -40% super lye is critical -- less lye does not reduce the goo/slime factor.
The water excess may also have something to do with reducing the slime/goo factor, but it definitely looks like it is the key for reducing the excess lye to safe levels. For about a week after the bars are first cut, the soap is unusually damp and cold from evaporation. This evaporation is transporting NaOH solution to the surface where some of the Na+ is reacting with CO2 to form soda ash.
But my calculations suggest the formation of soda ash can only be part of the neutralization process -- there is much more excess lye than there is soda ash formation (see photos). Being an engineer, I'm not content to just accept that this neutralization just magically happens. Unfortunately, my studies are not dredging up any clues about other routes of dealing with this lye excess.
Can you suggest any ideas for me to research?
Many thanks for considering my request -- I sincerely appreciate any help you care to offer.
Regards,
DeeAnna Weed, PhD
[I also sent pics of bars from the two batches I've made plus pics of the lather for both.]
***
Hi DeeAnna,
Wow, that's a lot of water for a CP soap. I'm surprised it sets up at all. As for the lye excess, my experiments with excess lye up to about 5% also show that the soap becomes tongue neutral over a few weeks. I have supposed that CO2 from the air neutralizes the excess lye, but I have not tested this. If I were to do this I would proceed as follows:
1) Cut identical bars from the superlye batch
2) let 1 bar cure in air as usual
3) seal 1 bar in a mason jar to exclude CO2 (this bar will not dry out)
4) the last test is a little more involved--you want to exclude CO2 but allow water to evaporate. If you have access to bottled nitrogen gas you could fit up a sealed box with a slow nitrogen purge. Otherwise, place the soap in a sealed container large enough to hold an open mason jar of dry NaOH. Over time the NaOH will absorb both water and CO2, allowing the bar to dry out.
5) from week to week, test a sample of each bar of soap for neutrality. The tongue test would give you some information, but if you want to follow the process precisely, titrate each sample to determine total alkalinity, as described in my book.
Please let me know what you discover. This sounds very interesting.
I am also surprised by the lather you are getting from this soap. I wonder whether it comes from the sodium carbonate. To test this you could knead a little sodium carbonate into a "slimy" castile soap to see whether the lather quality is improved.
Kevin M. Dunn
Professor of Chemistry
Hampden-Sydney College
***
Hello, Kevin,
Thank you for your kind and thoughtful reply!
I am setting up an experiment similar to what you propose. I thought about the design of the last test (item 4 in your email). I don't have the ability to create a dry nitrogen purge and I hesitate to use NaOH as a desiccant, so I think I will use a silica gel desiccant pack instead. I was looking for the old calcium chloride desiccant I used to use in the lab, but silica gel was easier to find locally. As far as doing TA analysis, no problem. I used to work in an industrial chem lab. It's going to be weird to titrate without a buret and all the other bits of lab equipment I used to use, but I'll get used to it!
As far as the lather goes, yes, the soap is lathering well, although it seems as if there is something on the surface of the bars that is interfering with easy formation of the lather -- maybe soda ash, maybe glycerin, maybe lack of water for bubble formation? I'm not sure. At times the lather seems scant and "ropy", but then it will develop a nice froth of bubbles as in the photo I sent. I'm not too concerned about it at this point, since most of our soaps are only 3 weeks old or less, but it will be something we will continue to test as the soaps get older.
And I agree with you -- this recipe calls for a LOT of water -- the final NaOH solution concentration is roughly 15% w/w. The abundance of water makes for some tricky moments during the mixing and molding. A few of us have had problems with the emulsion failing during trace or later when the soap is in the mold, but we're finding this is related to a couple of factors. One is any extra warmth created by over-insulating the molded soap or putting the mold in a 170 F oven to CPOP.
The second factor is too much agitation. Some of us getting the most consistent results by hand stirring only, but others are doing okay by mostly hand stirring and just lightly stick blending for short periods up to heavy trace. After that, it's safest to pretty much hand stir only until it's time to pour in the mold. We do know if the emulsion does break from stick blending that it can be re-established by going back to hand stirring. That seems counter-intuitive, but I'm thinking a fragile water-in-soap emulsion is able to form with only low-energy stirring, but the high shear from stick blending is breaking down this structure and allowing some water to separate from the batter.
I re-read chapter 15 in your Scientific Soapmaking book about the alkalinity tests you did on the 11 week old soap. It sounds like what you observed is what we're seeing with this recipe -- an unexpectedly large reduction in the alkalinity with time. I would not have expected remotely as much reduction as we're seeing, but our simple zap tests and handwashing tests are showing a striking decrease in the excess alkalinity.
I will keep you informed! Thank you for your insights and suggestions -- I appreciate the help in getting unstuck in my thinking.
Regards,
DeeAnna
***
So ... I'm back ... I'm in the process of gradually setting up an experiment or series of experiments to test this soap recipe. I'm open to your suggestions and ideas on how to proceed. Although I think Kevin's suggestions are worth following, I'm sure you folks will have good ideas to consider as well. Let me know!
Oh, and if anyone has a burette or a 125 mL or 250 mL Erlenmeyer flask collecting dust in the pantry, I'd be glad to buy it.
Some people use water straight out of their tap. DI water simply gives one less variable for things going wrong with saponification.
