Why do my soap turn out yellow after about 4 weeks?

[IDA]

I have done many soaps but this soap with lavendel turn out to be yellow on the out side.. Is it possible destroy soap?

 

[Arimara]

Care to post the batch's recipe?

 

[soapmaker]

Strange, but I just had a soap do that for me. I have been using the same recipe for 12 years and it never happened. The only variable was a different F.O. I think it had something to do with light because I cured the batch at my mother's house but kept a bar here at our house to watch the progress. Mine was cured out of light, hers was in light (not direct sun). Mine didn't turn yellow but hers did.

 

[DeeAnna]

Exposure to light will definitely change the color of soap over time due to oxidation. The yellow is basically rancidity (DOS). You can see this in Soapsmith's experiment: http://soapsmith.blogspot.com/2015/09/soapsmith-dos-experiment.html

I suspect what turned IDA's soap yellow might be the lavendel (lavender?) EO/FO. Some fragrances turn soap yellowish just because the fragrance is a darker color so it tints the soap. Sometimes the color is darker on the outside of the soap due to reaction with air or the loss of moisture. In this case, the darker color will extend deeper into the center of the soap as time goes on. The soap will otherwise look, smell, and feel fine.

Also oxidized lavender EO will trigger rancidity and rancidity will turn the soap yellowish, like the soap in Soapsmith's experiment. If the color change is due to rancidity, the soap is likely to smell musty or "off" and perhaps feel greasy or wet when the humidity is higher.

 

[IDA]

Thanks for the good info
I will send the recipe soon...
I will not have the next soap batch in light...
Thanks again

Care to post the batch's recipe?

200gr rapeseed oil
200gr cocosoil
200gr sunflower oil
Recipe

 

[soap1daze]

I never use grapeseed oil at more than 10% because of it's makeup. It tends to go rancid. I think it has a very short shelf life and is too soft of an oil to use that much. Not sure about the sunflower oil.

 

[soapmaker]

Exposure to light will definitely change the color of soap over time due to oxidation. The yellow is basically rancidity (DOS). You can see this in Soapsmith's experiment: http://soapsmith.blogspot.com/2015/09/soapsmith-dos-experiment.html

I suspect what turned IDA's soap yellow might be the lavendel (lavender?) EO/FO. Some fragrances turn soap yellowish just because the fragrance is a darker color so it tints the soap. Sometimes the color is darker on the outside of the soap due to reaction with air or the loss of moisture. In this case, the darker color will extend deeper into the center of the soap as time goes on. The soap will otherwise look, smell, and feel fine.

Also oxidized lavender EO will trigger rancidity and rancidity will turn the soap yellowish, like the soap in Soapsmith's experiment. If the color change is due to rancidity, the soap is likely to smell musty or "off" and perhaps feel greasy or wet when the humidity is higher.

Mine doesn't smell rancid at all. I've never seen a bar get yellow (mine is dk. gold/brown) all over. My F.O. was Galactic Grape from WSP. Very strong, smells wonderful! But I'm sure it was the light because I sit them in rows about 3/8" apart and it's the front that's the brownest. In between, not so much.

 

[IDA]

How do i now if my soap have been rancid?
It does not smell bad...

 

[zolveria]

grape seed culprit.. you should balance it with some hi oleic acid oil or add Vitamin E or use sunflower oil or safflower oil or rice bran oil

 

[soapmaker]

Rancidity stinks!

 

[IDA]

Rancidity stinks!

Thanks, does it just smell bad? Nothing else?

grape seed culprit.. you should balance it with some hi oleic acid oil or add Vitamin E or use sunflower oil or safflower oil or rice bran oil

Should i rebatch it with e vitamin? Do you mean that?

 

[nebetmiw]

Grape seed oil is a green oil and mixed with a plain sunflower will cause color change.
Rancidity will not always smell bad.

 

[soapmaker]

Grape seed oil is a green oil and mixed with a plain sunflower will cause color change.
Rancidity will not always smell bad.

I guess I just never had a rancid oil that didn't smell bad. Always can learn something new.

Thanks, does it just smell bad? Nothing else?

No that's not all, as has been said a colour change is another indicator. But in my experience the smell is the very positive indicator of rancidity and yellow spots. I have never had a soap turn yellow all over before.

 

[zanzalawi]

200gr rapeseed oil
200gr cocosoil
200gr sunflower oil
Recipe

i'm reading this as 200 grams of rapeseed oil, not Grapeseed oil, yes?

 

[IDA]

i'm reading this as 200 grams of rapeseed oil, not Grapeseed oil, yes?

Yes right

 

[nebetmiw]

Yes right

My bad sorry. But Rapeseed oil is a Yellow oil. Also very low shelf life. Have you made this exact formula before without yellowing? Have you use Rapeseed oil in soap before that was none colored?

 

[shunt2011]

Rapseed also has a very short shelf like. I wouldn't use it at more than 10% in a well balanced recipe. Could still go rancid but not as likely as in a high usage rate. I don't use it but some do successfully.

Did you ad FO or EO? Sometimes they will cause discoloration. How old is the soap?

 

[IDA]

My bad sorry. But Rapeseed oil is a Yellow oil. Also very low shelf life. Have you made this exact formula before without yellowing? Have you use Rapeseed oil in soap before that was none colored?

Yes i have done this before, and this never happened. With color and without. Shelf life? Do you meen the batch sustainability? I use Rapeseed oil in many soap. It that not correct? Do you use that? What do you for base in you soap?

 

[nebetmiw]

Yes i have done this before, and this never happened. With color and without. Shelf life? Do you meen the batch sustainability? I use Rapeseed oil in many soap. It that not correct? Do you use that? What do you for base in you soap?

Self life goes to oil not going rancid. Many car 6 months and should not be use in quantity. Other are over a year or more. You used equal amounts of 3 oils which two are known to have short shelf life. As was said Rapeseed oil is not used above 10% just for this reason.

My base is coconut, lard, tallow, palm and HO safflower or some other liquid oil. It's some combo using 3 or 4 of these. But I run a farm so my AOs are free as is my Goats Milk. I have the Soap Makers app to formulate my recipes instead of soap calculator. It gives break downs on how oils work and react. I play with my liquid oil alot as I have access to many good ones a decent price. I make one pound batches too most of the time because of the molds I use.

It took me a year to work a good formula that could handle liquid oil changes without fail. So don't worry we have all been there. First successes are normal and then trailers in one form or another. Even with same formula you will get weird things happen from time to time. Might be humidity, heat or cool even location can do it because air circulation is different. It's all in the fun of soaping.

 

[IDA]

Thanks for the lovely idea and the pepping to make good soaps.
Ok i will try to have coconutoil for the base instead. And not use so much rapeseed oil... Thanks again