Soap Gets Mushy When Wet...

Soapmaking Forum

Help Support Soapmaking Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


Well-Known Member
Aug 7, 2008
Reaction score
Philadelphia, PA
Here's the short version, I'm making soap using the recipe below. The bars are very hard and work well but when you set them in a soap dish, the little bit of water usually in the dish will turn the soap to mush. If there is 1/4" of water then the bottom 1/4" of soap gets mushy. If I let the soap dry then it turns solid again. I need to find a way to minimize this using natural ingredients. Any help would be appreciated.

Here's more details...
I've been making soap from the same used cooking oil I run my truck off of. I have plenty of it so I started making 4 gallon batches (~100 bars). I use 3.5 gallons of well filtered used cooking oil (soy and/or canola), 3.5 pounds of lye and ~20% water. I mix everything at ~120 - 150*F, whch isn't quite hot enough for hot processing but it only takes a few days to cure. I keep it well insulated and it stays warm for 1 or 2 days.

A day or two later I flop it out of the mold and cut into bars. It is so hard that it will crack if cut at room temperature. I made a "hot knife" out of steel which I heat over a gas stove. This works OK but still cracks the "soap ingot" at the bottom some times. The cut bars are not unusually brittle compared to store bought soap. It cleans well and lathers good.

Let me know what you think. Thank you.
As far as I know, *all* handmade soap gets mushy if it sits in water. The glycerin attracts moisture and soaks it into the soap. Best to let it dry out completely between uses. I keep all my soap on a wire shower caddy so it can dry out after I finish showering.
I'm short on time right now so I can't do the calculations for superfat, etc...but just soy/canola WILL turn out a soft bar, as far as I know. The harder oils lend soaps to harder bars, so people use them in combination.

Danielito is right, all soap will turn mushy sitting in water.

Do you know what superfat you're doing? Soap may also "feel" hard after a week, but moisture is still seeping out from the center of the bar to the outside. I'd give any soap a month or more before calling it cured, but that's just me. Some folks say a couple weeks, but I've never seen/tried their recipe.
Thank you for the replies. I do expect some softening but I'm surprised that it's more than the pure BioDiesel glycerin soap I also make.

I am not super fatting, the saponification value for soy/canola is 1 pound per gallon, so that's exactly what I've been using.
for starters, a 0% superfat is not brilliant unless you are using it to clean pots and pans. naturally the SAP of oils varies within a range and you risk a lye heavy soap. tho with used oils you would risk rancidity if you did superfat. anyway.

also, experience has shown me that it doesn't matter how you process your soap, you really do need a cure period beyond a few days. this will help the hardening & lastingness considerably.

but finally, tis the nature of true soap. but the degree does vary with the types of oils you have. and therein, I believe, is the difference between your biodiesel soap and your used oils soap. canola and soy both tend toward slimy if used at high levels.

The way to get past it its simply to use a soap dish that drains.
palm oil or bees wax should avoid the "mushy gelly problem". (I'm not a good tester because I hang my soaps under the mirror, so they get dry and don't get gelly)
Another great stuff is a "grilled soap holder" (sorry, English is not my first language, but something like the one you can see in the first picture here ) will solve the problem, too.
Choosing hard oils like palm or including beeswax might help a tiny bit, but nothing overcomes leaving soap in water. Soap dissolves in water.

I make soaps with 100% hard oils, I've made 100% shea butter soap and with 100% cocoa butter. Soap that sits in water becomes mushy. It's soap.
carebear said:
Soap that sits in water becomes mushy. It's soap.

yes, of course soaps dissolve in water, but if I leave supermarket soaps on the corner of the corner of the basin, it doesn't get that transparent fluffy gel, if I leave a homemade soap there, it does (I've tried just once, by mistake, with a 100% olive oil).
But supermarket soaps last less than homemade ones.
:lol: the 'transparent fluffy gel' is glycerin; they take that out of supermarket soap, cause it's pretty expensive & good for your skin. Mostly put in cremes and stuff.
I'd say:
less water discount to make sure your soap won't crack during cutting.
cutting before the soap is too hard
use of a hard fat like tallow, lard or crisco, to make the soap less slimy when wet.
at least some superfat,cause what you are doing is just irrisponisble when you sell or give away your soap.
and finally a good oldfashioned cure -with your CP at least 3 weeks-.
Saponification is a process and you can not hurry it.
As everyone said, put your soap in a place were it can drain, wether it's a wire shower caddy or a proper soap dish.
commercial soaps. They may actually be detergent bars, but even if "soap", they aren't made the way yours are. Commercial soaps are compounded from de-glycerinized saponified fatty acids - your soap has glycerin. Commercial soaps are compressed under very high pressures making them much more dense than yours are. And they may contain hardening agents as well.

While hard oils and a good long cure period help on the lastingness, it's undone by leaving it in a puddle of water. Your soaps are different. Period.
Thanks folks!
I've been making all my own soap for a couple years now but haven't used any other natural soaps... so I wasn't sure if ti was just mine from using soft oils.

Regarding being hard and cracking when cut, on my most recent batch (2 logs making 90 bars) I cut it the next day and it was still soft enough that it was easy to cut.

About it being from the glycerin in the oil, I also make soap from BioDiesel glycerin, which is ~90% glycerin and the rest being free fatty acids. This soap does get soft when it sits in water but not nearly as soft as soap made from the same whole oil. Ironically, it is a softer soap.
carebear said:
Commercial soaps are compressed under very high pressures making them much more dense than yours are.

cause i've been thinking about a cylinder vise to compress grated soap.
Anyone tried it?
How much pressure?
Why can't i win the lottery?
You'll need more force that that I think - even at 750lbs, this machine makes bars which aren't hard enough for use, according to them.
The model LS-H is a bench top soap press used for stamping small bars such as those made on the LE-2 and LE-2.5 machines. This machine is hand operated and exerts approximately 750 pounds of force. It is useful for evaluating small bars for general appearance but not recommended for producing bars which must stand up under a "wash-test". The LS-H can be affixed to a table top with bolts or alternately can be temporarily fixed with an optional clamp.

Our lab (where I work) has a pneumatic soap press.

These offer 1 ton or 6 tons of force, depending on the machine. But only press out one at a time.
I have a shop press which I want to try compressing soap with some day. It's a small one but it's still rated for ~10 tons. The main purpose of this experiment is to make nicer formed bars and/or recycle end pieces.

I found that the reason our soaps get soft in water is the glycerin. Even soap from unsaturated oils stay fairly hard if you separate out the glycerin.