After being
very surprised with the differences between my own pH testing of my bar soaps, and
the lab results from the batch analysis, I continue to experiment. I have also purchased a digital pH metre
which has become necessary for developing great liquid soap.
I went into
the studio today just to do some pH testing and unfortunately the
pharmacist/chemist/technical advisor that works with me sometimes, was not with
me today. She would have been a great
help. We have done some testing together
but not since I got my pH metre.
Important
to note:
-
My
results in testing bar soap can’t be that exact as I am testing a solution of
distilled water with soap bits mashed up in it.
(Liquid soap testing is much more exact.)
-
I
am not a chemist and am learning from experience and experimenting, not from
exact studies.
-
I
am not really obsessed with the pH in my bar soap. As long as it tests between
9 and 10, and even sometimes slightly over 10, I am fine with it. They are wonderful for the skin. I know that. I have heard of some soapers claiming they
achieve as low as a 7. That is not
something I am aiming for. I work
together with the lab who advise me what is okay and not okay in my results.
Let’s look
at the testing for some of my different soaps.
First I tried a Castille soap (only olive oil and water). On the right, the soap is 5 months old. On the left the soap is one month old. I only saw a slight pH difference between
these two soaps, which struck me as strange and they also seemed to test high all
around. For the phenol (Phenolphthalein) test, from the pink,
we can see they are over 8, but don't look over 10.
Do they possibly look around 9?
On the far paper strips, the older soap looks around a 7.5? And the younger soap looks around an 8.5? On the closer paper strips, they both look
around a 9? With the digital ph metre,
they both tested slightly over 10. I
don’t have the lab results back yet.
Orange
Poppyseed soap on left. Lemon Sea Salt on right. Both finished 8 week curing period. Phenol makes the pH look quite low, the
orange one around 8 or 8.5 and the lemon sea salt soap looks below 8! On the paper strips you can see on the far
strips, the lemon salt soap looks around 7 and the orange poppyseed soap looks
around 8. On the other paper strips,
they both look the exact same around 8 or 9.
Then the pH tests the lemon sea salt soap in at 9.78! and the orange
poppyseed soap over 10 – which surprised me because both of these citrus soaps
are usually the ones that test lowest on pH from the lab (still always over 9).
So, I
calibrated the pH metre again in the 7 and 10 buffer fluids just to make sure
everything was right.
Here is my
Green Clay-Aloe Vera soap that was made last August. You can see the results here. Phenol looks around 8.5? Both pH strips look around
8 and digital pH reading is 9.69.
Now for making
liquid soap, it seems like more of an exact science because I can lower the pH
to exactly what I want. As you can see here, from the phenol, it looks like the
pH is lower than 8, the paper strips look around 7 and the digital meter
reading is 9.29. It first came in over
10, so I lowered it to 9.29 which is right around where I want it.
Conclusions
so far from my own testing:
-
The
various home-pH-testing methods produce wide differences in results
-
PH
results vary even between different testing-papers
-
PH-testing-papers
produce falsely low results
-
Phenol
seems to be the most difficult to deduce an exact pH
-
The
digital pH-metre tests even higher than the lab results, but the closest to the real pH
(assuming the lab results are real)
-
In
my own testing I only trust the pH metre
-
In
reality, I only trust the lab results
Ever had
your soap tested by a lab for pH and free lye?
All of the batches that I sell have to be tested. The results are fascinating and I learn a lot
from them.
Questions
to you – What pH are you aiming for in your bar soap? Liquid soap?
Do you try to lower the pH in your bar soap and with what methods? Anything else you can contribute to help soapers all over would be awesome!!
Happy soaping and pH testing!!
xo Jen
