Newbie questions after 4 batches

[RacerSpuffy]

I decided to get into soap making for a few reasons, the biggest reason is that I hoped to make some soap that would help with seasonal dry skin. For much less important reasons I thought it might be cool to give some away to my family and friends. I'm not looking to do this on any large scale or go into selling. Hobby/curiosity and not a job

I have a fair bit of experience both in graduate school and in professional life working with very concentrated acids and bases so I was comfortable with CP soap making. In fact, I thought I was comfortable with HP too but after watching some videos on that I've decided I won't attempt that until summer time and I can do it outside.

Everything I have made so far has gone into a 6 bar 4oz/bar silicon mold.

On to what I have done and my questions:

Batch 1:This was a very 'fly by the seat of my pants' type make. I use SoapCalc and didn't pay any attention to the ranges suggested to stay within, I also didn't really think things through on the volume I was making and came up a bit short at only 3.75 bars.

Ingredients:
Coconut Oil (76) - 227g (80%)
Olive Oil - 57g (20%)
Lye - 47g
Distilled Water - 108g

I did this with a cheap scale, so while SoapCalc gave me to decimal places I just rounded to nearest gram. I also don't have a stick blender/immersion blender so I just hand whisked it.

I mixed the oils into the lye water when both were at about 115F. I whisked by hand while keeping the temp between 115 and 130F as read by an IR temp gun. After about 45 minutes I was getting a pretty decent trace and I dumped in a bit of wet coffee grounds (for 2 reasons, one was I wanted a bit of 'pumice' to it and also thought it might kill the garlic scent that turns out my olive oil had in it). I poured into the mold and the last 0.75 bars had to be removed with a spatula since it was about the consistency of pudding at this point. I then covered with plastic wrap and a light towel. 16 hours later I removed the bars and was pretty happy with them.

Batch 2: Was so pleased at how simple things worked on Batch 1 I went out and got some more ingredients and scaled things up enough to fill all 6 slots in my mold.

Ingredients:
Morrell Snow Cap Manteca (Lard) - 200g (50%)
Kroger Pure Canola Oil - 100g (25%)
Coconut Oil - 100g (25%)
Sodium Hydroxide - 57g
Distilled Water - 152g

Mixed at same temperatures as batch 1, hand whisked. Took forever to get to trace, in fact I'm not sure it really ever did what I'd consider a trace. However I'm certain there wasn't any separation of oil and lye-water after 30 min (probably sooner). It got to perhaps a weak trace at 110 minutes of whisking and frankly I was tired of dealing with it at this point. I added a small amount of essential oils (guessing about 0.05g) so I poured it and covered like Batch 1.

On removing from the mold ~20 hours later, a bit stuck in the corners but whatever it came out mostly good. Much whiter than Batch 1, but I used different oils and didn't add any coffee so figured thats how it should be.

Batch 3: Ok, at this point I realized my numbers are way out of suggested range for Batch 1, and Batch 2 just by luck seemed to fit in the number ranges on SoapCalc just fine. I also have read a bit more at this point and attribute the slow trace time to the low lye concentration in Batch 2. So I decide I'm going to bump my lye concentration up to 35% for this one. I play around with SoapCalc and different fat sources again and decide on 4 sources.

Ingredients:
Morrell Snow Cap Manteca (Lard) - 120g (30%)
Kroger All Vegetable Shortening - 120g (30%)
Coconut Oil - 120g (30%)
Filippo Berio Olive Oil - 40g (10%)
Sodium Hydroxide - 56g
Distilled Water - 104g

Mix at same temps as Batch 1 and 2, but this time I have decided I don't want to hand whisk for 2 hours anymore. I also didn't want to spend $30 for an immersion blender, so I bought an 88 cent whisk and cut the hanging loop off the end and mounted it in my drill. Expecting a fast trace because I used higher lye concentration and am now mechanically stirring rather than by hand. After an hour and a half of no trace or extremely minimal I give up because I have somewhere to be, so I add a tiny bit of food coloring (that was gel type and didn't mix well, but actually the result was kinda cool) and the same amount and same type of essential oil as before. Pour in mold, cover as before. 20h later I remove from mold and it breaks up a bit more on the edges than batch 2 which is somewhat concerning but I'm not terribly upset.

Batch 4: I'm not happy with the long time to trace and I'm not crazy about how much bar is sticking in the corners/edges of the mold - its not terrible, but after how well the first ones came out I'm disappointed. So, with that in mind and knowing now about wanting to keep the soap qualities in the suggested ranges I find that if I essentially flip the oil amounts around from Batch 1 I can get a more rounded bar. Also based on my experience thus far I figure it I can probably take it to family over Christmas and even though I know it isn't ready to be used, I could probably give a few bars out and tell them it still needs to dry/cure. So I set forth with this:

Ingredients:
Filippo Berio Olive Oil - 338g (75%)
Coconut Oil - 113g (25%)
Sodium Hydroxide - 63g
Distilled Water - 117g

Mix just like what I did with previous batches. This time I mix by hand again based on time to trace not being improved with drill whisking, I figure I'll try and speed this up by mixing at 120-130F. After an hour and a half of whisking I get discouraged, and pour it into the mold. I figure its fine, the earlier ones didn't trace well either and I had no separation issues. I had this in a box that nearly perfectly fit my mold so I cover with aluminum foil, and then wrap the box in a couple towels and let sit for ~4 hours. Then its time to travel, I didn't peek at the soap because it didn't matter, I wanted to bring this to family so it was going to work or not, peeking wasn't going to change anything. I transport it, bring it inside when I get where I'm going and it sits 24 hours before I look at it. When I look at it, some of it slopped around during transport but its mostly ok, however it is way too soft to remove from the mold. I attribute this to the room temperature being about 57F rather than ~68 that my other soaps were at. 48 hours later I am able to remove it, and there is a more white base and the top half is more 'wet' looking. I still don't see any oil/water separation so I figure it is probably ok.


My concerns/questions:
Is what I've described typical for the blends I made?
Why does Batch 1 look different (aside from the coffee)? - batch 1 looks like maybe it partially gelled, but not actually sure that happened.
Batches 2-4 are all a bit crumbly on removal from the mold, batch 1 was not.
Why did Batch 1 thicken up like I expected based on what I'd seen in youtube videos from various people but Batches 2-4 not?
Is the stick blender the key here on getting to trace faster? Is 90+ minutes typical?

I know this is a huge first post for a newbie. If there is anything more you want to know just ask. I did create a spreadsheet for each of these, including bar weights so I could monitor drying over time.

 

[earlene]

Welcome to the forum, RacerSpuffy. I am hobbyist soapmaker as well, with no plans of selling, but give a lot away because it's so much fun to make.

Congratulations on your first 4 batches.

Looking at your recipes, though, I am wondering what your skin is like (age, condition, etc.) because for me, those high cleansing numbers you'd get with that much CO, would simply not work for my skin. I am what some may call elderly, although to me, I am forever young. In any case, my skin doesn't tolerate high Coconut Oil soaps well. But some folks handle it just fine.

Have you had them long enough to cure sufficiently so you know how they perform for you yet? Even new soap with a gentle-to-my-skin recipe will be too drying until the soap has cured long enough.

Regarding batch number 4, with a high percentage of high oleic oils, like Olive, it can take a really long time to come to trace and you need to do a lot of stirring. That's why a SB is a soapmaker's friend. It takes far less time than hand stirring. I have read of people spending a good 2 hours stirring by hand. But you don't have to stir the whole time. You can stir for a few minutes, walk away for 20 minutes, come back and stir some more, repeat until you get trace. The lye has to start working on the oil, but it also needs to be mixed periodically to reach and maintain a stable emulsion and trace before you mold the soap. Lard is also a slow-to-trace oil, so that's why #2 & #4 took so long.

I bought a perfectly useful SB at Walmart for only $13.00 that I use when I travel, which I keep in my travel soaping bag. So you don't have to invest in a high-end SB. Just don't over-use it and use only short bursts so the motor doesn't overheat and burn out.

I don't do a lot of lard soap, but I understand it is also slow to

 

[earthling121757]

Hi Spuffy, I'm a newbie too but I'll give you my opinions.

Batch one with the 80% coconut oil will trace a lot faster than the other ones. It also hardens in the mold quicker and if you wait too long can break when cutting. Lard and olive oil tend to trace very slowly (in my experience) and I use a high lard recipe when I want to divide and mix different colors to play with swirling techniques.

Also, I highly recommend a stick blender. The high shear of those blades really helps with getting the emulsion and trace going, which you can't really get by hand wisking or even drill wisking. I bought a $10 Walmart two speed stick blender and it's been working great.

Also, if you're not in a hurry don't try to un-mold too soon, just leave it for two or three days and that will help with the tearing on extraction.

 

[RacerSpuffy]

Thanks for the reply. I have not used any of the soaps I made yet.

Batch 1 - Out of mold on 12-17-17
Batch 2 - Out of mold on 12-18-17
Batch 3 - Out of mold on 12-22-17
Batch 4 - Out of mold on 12-25-17

Thanks for the information about the SB, I'll look for it next time I'm at Walmart. I just didn't think that a few bursts of a SB is mixing so much more effectively than me by hand or whisk in a hand drill, but maybe it really is.

I could completely drop coconut oil out of future makes, the only reason I've used it in all of them so far is it is key for cleansing according to SoapCalc so if I don't use it, I'm having trouble finding enough cleansing with any of my other oils. However, since I've not used any of these, maybe I don't even need cleansing...

 

[DeeAnna]

Here's why a stick blender is so helpful --

Fat and lye solution don't want to stay mixed together if left to their own devices. If you just left the pot of fat and lye solution alone without doing any mixing, a layer of soap will form where the lye and fat layers touch. Once enough soap forms at this interface between the two layers, the saponification reaction will basically stop because the soap layer insulates the lye from the fat.

When you use low-intensity mixing such as a whisk or spatula, the surface area between the immiscible layers is increased compared to the no-mixing experiment, because the whisk breaks the two layers into smaller globules. More surface area means the soap can form a little faster. Also the mixing breaks up the soap so it doesn't "insulate" the fat and lye from each other. Problem is that low intensity mixing is labor intensive and once you stop mixing, the globules of fat and lye quickly revert back to two layers. This is how my grandmother made her lye soap, and yes it took hours of on-and-off stirring.

Stick blenders are high intensity mixers. They break the fat and lye into very small droplets -- lots of surface area. This increases the rate at which the soap will form. The high intensity mixing also breaks up the soap into small particles that act to combine the fat and lye droplet into a stable emulsion. Once a stable chemical emulsion forms, the mixture no longer has to be mechanically mixed. This emulsification happens when soap is whisked by hand as well as when it's stick blended, just that it can take longer to get to that point with whisking, sometimes a lot longer.

Some people use hand-held or stand mixers (the kind you'd use to make cookies or cake) or regular types of blenders. The mixers aren't quite as high intensity as a SB'er, but they sure save your arm muscles. A regular blender is similar to a stick blender in the intensity of mixing and it can work quite well for smaller batches.

The reason why your first recipe went so well is the high percentage of coconut oil, which saponifies easily at low lye concentrations. You used 27% to 35% lye concentration for your other batches. If you wanted to keep using a whisk with recipes like the later ones, I'd suggest using a higher lye concentration -- anywhere from 40% up to 50%. I'd also use somewhat warmer starting temperatures for the soap batter -- maybe something closer to 150-160 F would be my guess.

The point here is if you don't have high intensity mixing as a driver for saponification, then higher lye concentration and increased temperatures are going to help. Another option is to add an accelerant like a bit of clove essential oil -- the eugenol in clove EO is the accelerant.

edit: The soapcalc name of "cleansing" is just plain wrong. All this number means is the % of myristic and lauric acid in the recipe. These fatty acids help form big fluffy bubbles that many people like. They also make a soap that is very soluble in hard, salty, and/or cold water. If you bathe in warm, softened, not-salty water, you don't need a lot (or even any) lauric and myristic acid to make a soap that cleans just fine.

Another issue for myristic acid in particular and lauric acid to a lesser degree is that soap made from these fatty acids can strip the skin of its normal fats and proteins in the non-living surface layer of the skin. For people with normal skin, a soap high in these fatty acids can leave the skin stripped and dry feeling, especially in winter. People with sensitive skin may find their skin will get reddened, flaky, and even irritated.

 

[RacerSpuffy]

Thank you DeeAnna for the extensive reply. Suppose it is worth getting a stick blender. I've seen and read plenty of things to know to be cautious about burning them out, so I'll use them initially and then go to whisking by hand if necessary later.

I was thinking about bumping up lye concentration but I didn't know what to bump it up to. The entire reason I went to 35% for the last 2 batches was because of the time to trace difference between my first 2 where I went with the default 38% water to oil thing and noticed that my first lye concentration then was 30% on batch 1 and 27% on batch 2. Then my inexperience and switching oils prevented me from making a good conclusion on whether I should go higher than 35%. I think I may hold at 35% and try a very similar or the same to something I've already made, but use a stick blender next time.

 

[penelopejane]

Thank you DeeAnna for the extensive reply. Suppose it is worth getting a stick blender. I've seen and read plenty of things to know to be cautious about burning them out, so I'll use them initially and then go to whisking by hand if necessary later.

I was thinking about bumping up lye concentration but I didn't know what to bump it up to. The entire reason I went to 35% for the last 2 batches was because of the time to trace difference between my first 2 where I went with the default 38% water to oil thing and noticed that my first lye concentration then was 30% on batch 1 and 27% on batch 2. Then my inexperience and switching oils prevented me from making a good conclusion on whether I should go higher than 35%. I think I may hold at 35% and try a very similar or the same to something I've already made, but use a stick blender next time.

You will not burn your SB out if you use it to gently mix your ingredients and not beat them. Watch the following video:
[ame]https://www.youtube.com/watch?v=39pLHKMtN6o[/ame]

 

[DeeAnna]

Thank you DeeAnna for the extensive reply. Suppose it is worth getting a stick blender. I've seen and read plenty of things to know to be cautious about burning them out, so I'll use them initially and then go to whisking by hand if necessary later....

What Penelopejane said. You do not need to use a SB'er much to get great results. A little goes a long way. I normally use a SB for maybe 5 seconds total per batch in several bursts over a period of 2-3 minutes total. This is a whole LOT less stick blending than most beginners think is required.

Always, always err on the side of SB'ing less rather than more especially at first. After a few short bursts over the first few minutes, just hand stir for awhile, and see how things go. If needed you can SB a little more, stir by hand awhile, and so on. This will give you the best control over the soap making process ... and you won't remotely come close to burning out your stick blender.

The reason why you want to use just enough stick blending but not overdo it -- Once you get the soap batter finely divided into tiny droplets with a stick blender, it will take a lot longer for those droplets to coalesce back into two layers compared to droplets made just by hand whisking. While those droplets are clumping back together, the lye and fat are also reacting into soap.

It's a bit of a race between the two competing actions. With stick blending, just a few seconds of mixing are really all that's needed, however, to make small enough droplets that won't coalesce too quickly. You can get to this point with only a few judicious bursts of stick blending separated out by some gentle hand stirring and scraping of the sides of your soap pot.

By stick blending so much that you risk burning the SB'er out, you're really not accomplishing anything besides revving up the saponification reaction so much that your soap reaches trace too fast. Sometimes you want to rev up the saponification reaction, but wait until later in the soap making process to make that decision to SB more to get saponification to pick up speed.

If you follow the trials and travails of the new soapers here, you'll see stick blending too much is one of the top 5 reasons why new soapers have trouble making decorative swirls and have to "glop" their too-thick soap into the mold. This finesse with a stick blender is just part of learning soap making -- just something a person has to find out by experience.

...I was thinking about bumping up lye concentration but I didn't know what to bump it up to. The entire reason I went to 35% for the last 2 batches was because of the time to trace difference between my first 2 where I went with the default 38% water to oil thing and noticed that my first lye concentration then was 30% on batch 1 and 27% on batch 2. Then my inexperience and switching oils prevented me from making a good conclusion on whether I should go higher than 35%. I think I may hold at 35% and try a very similar or the same to something I've already made, but use a stick blender next time.

If you use a stick blender, I'd stick with the lye concentrations you are currently using. You can go higher, but there's no real need to. The only type of soap I'd go higher on is a 100% olive oil soap or other recipe very high in oleic acid. In that case I'd maybe use 40% lye concentration. But recipes with a balanced blend of fats do quite well at about 33% lye concentration, give or take a few percent. Recipes high in coconut oil and similar high lauric-myristic fats do better with a lower lye concentration -- 28% or so.

 

[MorpheusPA]

I'm Johnny-Late-To-The-Fair here, but I'll chime in. Get a stick blender.

I did hand-mix once to experience soap making something like my great-great-grandmother would have. Once. It was so frustrating that I understand why great-great-grandmother bought her soap. What takes hour upon hour when hand mixing happens in a minute or three when using the stick blender!

 

[RacerSpuffy]

I bought a stick blender today , won't have time to make any soap tonight. I may re-make one I've already made just so I can have a direct comparison.

It is supposed to be ridiculously cold the next few days so I should be able to get in at least 1 more batch.

Thanks for all the replies and information.

 

[SaltedFig]

Congratulations on your new adventures and soapy purchase!

I had this in a box that nearly perfectly fit my mold so I cover with aluminum foil ...

Aluminium is dissolved by lye, so it is best to avoid this metal completely when you are making soap (no aluminium trays, molds or foil).

This topic (from earlier this year) has some good tips in it:
What advice would you give to your beginning soaping self?

 

[RacerSpuffy]

That was intended to be a transport box for a one time use, I anticipated the soap to not be as firm as it should be so foil was used to reflect the heat back in rather than plastic wrap and towels. I foiled and then covered the box in towels (box was 2" tall). it worked out fine, yes aluminum and lye react however (and I know this gets dangerous territory comparing differing industries vs expert soaper's experience), I worked in aerospace for several years with metal finishing (and am a geochemist by schooling) where most of our work was on aluminum and titanium. The reactions happening with lye and the oils are killing most (and eventually all) of the lye - aluminum solubility is extremely low as you approach neutral pH, so simply covering a mostly reacted mixture (at least on a log type scale like pH) with foil is going to be fine. Mixing up your lye in an aluminum pot and doing initial blending with aluminum blenders, then yes, absolutely I agree with you.

 

[penelopejane]

I worked in aerospace for several years with metal finishing (and am a geochemist by schooling) where most of our work was on aluminum and titanium. The reactions happening with lye and the oils are killing most (and eventually all) of the lye - aluminum solubility is extremely low as you approach neutral pH, so simply covering a mostly reacted mixture (at least on a log type scale like pH) with foil is going to be fine. Mixing up your lye in an aluminum pot and doing initial blending with aluminum blenders, then yes, absolutely I agree with you.

I’m not a scientist but if any metal touches soap, even after it has saponified and cured, then you will risk getting DOS on the soap. DOS - dreaded orange spots - very scientific term - is the beginnings of rancidity which spreads until your soap is a puddle of yellow gloop.

DOS can be spread in a number of ways but keeping metal away from your soap is an easy way to avoid one common source.

 

[toxikon]

I'd stick to parchment paper instead of foil.

One thing I thought I'd mention is the fact that soap calculators have a few different ways to calculate the amount of lye and water in your recipe.

The default is usually "water as % of oils", set to 38%. This is considered a lot of water, and equals out to about 25% "Lye Concentration".

Most of us on the forum disregard the default and only use "Lye Concentration" or "Water to Lye ratio".

Lye Concentration can range anywhere from 25-50%. If the lye is any higher than 50% (with your water making up the other 50%) it won't dissolve.

Most people use around 33-35% Lye Concentration for general, balanced recipe. A recipe high in olive oil can benefit from a higher Lye Concentration of around 40%.

A Lye Concentration on the lower end, 25-30%, should usually be reserved for hot process, as it requires more fluidity than cold process.

Hope that helps.

 

[RacerSpuffy]

I’m not a scientist but if any metal touches soap, even after it has saponified and cured, then you will risk getting DOS on the soap. DOS - dreaded orange spots - very scientific term - is the beginnings of rancidity which spreads until your soap is a puddle of yellow gloop.

DOS can be spread in a number of ways but keeping metal way from your soap is an easy way to avoid one common source.

That is interesting, noted.

I'd stick to parchment paper instead of foil.

One thing I thought I'd mention is the fact that soap calculators have a few different ways to calculate the amount of lye and water in your recipe.

The default is usually "water as % of oils", set to 38%. This is considered a lot of water, and equals out to about 25% "Lye Concentration"...

...Most people use around 33-35% Lye Concentration for general, balanced recipe. A recipe high in olive oil can benefit from a higher Lye Concentration of around 40%.

A Lye Concentration on the lower end, 25-30%, should usually be reserved for hot process, as it requires more fluidity than cold process.

Hope that helps.

Yeah, I went with that water as a % of oils the first 2 batches, after that I did 35% lye concentration.

I have a new question now.

When the bars are curing in this 4-6+ week window, I assume room temperature is what is recommended. What happens if this temperature is increased or decreased? I have a finished attic that has my HVAC vents to it shut off, it never gets more than 110F up there (summer), but it can get pretty cold (down to 45F - winter). What would that do to the curing time or the quality of the bars?
I'd guess that the colder it is the longer it would take, and obviously avoid freezing especially when bars are still losing water weight, and maybe some soaps might sag/melt if the temperature gets too high.

 

[MorpheusPA]

Curing will take longer at colder temperatures, but you'd have to test that and it's going to depend on the humidity in your attic as well. Ditto for summer, although hot, dry days should tend to speed up curing on average.

Bar slump at 110° won't be an issue, it has to get hotter than that!

 

[earlene]

I have found that my soaps curing in my upstairs (less AC available in those) rooms during a hot summer tend to develop DOS faster (if they are going to develop DOS) than if I keep them in a more comfortably somewhat cooled room downstairs. My attic is even hotter in the summer, so I would not cure them there. But you attic may be more comfortable than mine in the summer. Still 110° F is too warm IMO for extended periods when it comes to curing soap.

When I say 'more comfortably somewhat cooled room' to me that is in the mid to upper 70's, even low 80's °F range in the summer.

As to cold and how it affects cure, I have not experienced colder than high 50's - low 60's °F range in the winter. But since I always prefer a longer cure, and because I have so much soap that a long cure works well for me, I am not sure that it matters much.

What I have found that makes a pretty significant difference is humidity. It seems as though high humidity slows things down a bit, as well as causing some soap to sweat.

 

[The Efficacious Gentleman]

I wonder -

Colder air is denser, and curing involves (in part) the transfer of moisture from the soap to the air. If there is less "space" in the air, can less water transfer out?

 

[penelopejane]

When the bars are curing in this 4-6+ week window, I assume room temperature is what is recommended. What happens if this temperature is increased or decreased? I have a finished attic that has my HVAC vents to it shut off, it never gets more than 110F up there (summer), but it can get pretty cold (down to 45F - winter). What would that do to the curing time or the quality of the bars?
I'd guess that the colder it is the longer it would take, and obviously avoid freezing especially when bars are still losing water weight, and maybe some soaps might sag/melt if the temperature gets too high.

The problem with high temps is that the soap might sweat and this might lead to DOS or some other problem. I have my soap curing in a room that is a pretty constant temp year round but the airflow isn’t great (no window) and I’ve noticed this summer (put shelving in the room has inhibited airflow) that my soap is sweating and not just the salt bars. I’m using a fan on hot days that seems to work except (although it helps a lot) for the salt bars. Salt bars take 9 months to cure and require regular changing of a towel they are sitting on as they sweat for 6 months under normal conditions. It been up to 100*F here outside but nowhere near that inside but it’s the lack of airflow and humidity that’s the killer.

High heat you are talking about will speed rancidity in your soap. Handmade soap isn’t as stable as commercial soap and has no preservatives. DOS is not a huge worry if you follow basic hygiene practices for your soap (I’ve never had it - touch wood) but I’m very careful even to the point of using gloves to move my curing soap. My soap is high OO so requires long curing/holding times so I do everything I can to make it last in pristine condition.

I am in the process of moving my curing soaps as using a fan is annoying and unsustainable.

Fluctuating temps (because the heat won’t be evenly distributed) are also likely to warp your bars. Higher water in your recipes might lead to this too but I soap at 31-32% lye concentration even for pure Castile soap and I don’t have a problem with warping.

I’d choose a room where the temps are fairly stable and you get good airflow for a good cure. Maybe a basement?

 

[Kittish]

That was intended to be a transport box for a one time use, I anticipated the soap to not be as firm as it should be so foil was used to reflect the heat back in rather than plastic wrap and towels. I foiled and then covered the box in towels (box was 2" tall). it worked out fine, yes aluminum and lye react however (and I know this gets dangerous territory comparing differing industries vs expert soaper's experience), I worked in aerospace for several years with metal finishing (and am a geochemist by schooling) where most of our work was on aluminum and titanium. The reactions happening with lye and the oils are killing most (and eventually all) of the lye - aluminum solubility is extremely low as you approach neutral pH, so simply covering a mostly reacted mixture (at least on a log type scale like pH) with foil is going to be fine. Mixing up your lye in an aluminum pot and doing initial blending with aluminum blenders, then yes, absolutely I agree with you.

Almost right. Couple of points you may have overlooked. First, is that when soap is first made, and for the first couple of days it's still got quite a lot of unreacted lye available. So, your batch wrapped up for transport, especially if it was soft enough to slosh, had very much enough lye available to cause a really nasty reaction with the foil if they had come into contact. Second, is that the pH of soap never does approach neutral, it stays very firmly on the alkaline side. I don't know what effect, if any, that would have on the solubility of aluminum, but it should probably be taken into account.