Is the silicone mold causing this discoloration?

[MaryWaldman]

I use the Brambleberry 12 cavity rectangular silicone mold for my cold process soap line. After each use I wash them in cold water, a little bit of dish detergent, rinse them, and allow them to air dry. I've never had a problem with this method, and have been using this set of molds for two years with no issues.

Suddenly my CP soaps have been coming out with a strange tan/orange color over them. At first I blamed older coconut oil but using fresh gave the same result. Then I blamed the FO's, but a batch with no FO gave the same result.

Finally I poured a few bars of Stephenson's Melt & Pour goat milk soap that I had around with no FO. I've done this before and unmolded pure white bars, but this time you'll see in the attached pictures the yellow/orange film. I sliced one open so you can see the discoloration.

This is a very serious problem for me - does anyone have any idea what's going on?

As well:
- We are on well water, which is filtered and hasn't had any changes. I also washed the mold in bottled spring water and patted it dry before the M&P pour.
- Room temperature was 68 degrees
- I let the M&P cure for 24 hours at room temperature in the mold wrapped in a towel, the same as I would for CP.

 

[jcandleattic]

I'd say it's probably the mold. Silcone will degrade over time, and that's probably what's happening. Just a guess though as I'm no expert on silicone.

 

[Cellador]

Maybe this is just something I notice, but FOs tend to linger on my silicone molds. Have you recently used a discoloring FO in the mold?
Have you tried these recipes/ingredients in another mold to see if you have the same issue?

 

[MaryWaldman]

The lingering FO might be an issue... but I haven't changed up my FO's in a while. They are all under a year old.

And I just unmolded a batch of my foot exfoliating CP soap yesterday in its dedicated mold (about 2 years old, about 15 batches) and it's doing the same thing. BADWORDS. I only use The Sage Peppermint FO in this.

The picture shows the mold, the discolored soap, and a bit of left over I poured into a clean plastic pan which is fine.

 

[jcandleattic]

I still believe it's the silicone. When you pull/stretch the silicone does it look like white stretch marks? If so, that's the silicone degrading, and I am sure that will cause discoloration of the soap.

I have a rose soap mold made of cheap silicone and after about a year it did the same thing as the first pic you posted. I finally determined it was just from the degrading of the silicone causing it.

 

[MaryWaldman]

I still believe it's the silicone.

I have to agree with you. I will try the stretch test.

 

[BrewerGeorge]

Does the yellowish part zap? Does it go away after a short cure?

 

[MaryWaldman]

Zap test - the Goat Milk M&P didn't zap (and is actually kind of sweet). The CP had no zap.

The yellowing seems to get worse with age, even after they've been out of the molds. My process is: pour CP, put to bed for about 24 hours at room temperature. I sometimes put a tray in the freezer for a few hours to help with release but not always. I unmold on the third or fourth day.

Stretch test - the two molds (pink and blue) didn't show any white when I pulled them.

I am doing a test right now with every silicone mold I own. They are all clean, some have never been used, and the oldest is 3 years old. None have ever had colorants. I have poured about 1 tablespoon of the Goat Milk M&P (with no FO) into each mold.

After 1 hour everything is nice and white, even in the two problem silicone trays. We'll see what happens overnight.

Results of the Goat Milk M&P test:

I poured 1 - 2 Tablespoons of new Goat Milk M&P with no FO or colorant into each silicone mold I own (see picture).

All three blue Brambleberry 12 rectangle molds caused discoloration.

The rest, including the pink 6 rectangle I use for test batches of everything, had no discoloration.

The pink 6 oval that had discoloration with the salt bars (see above) did not discolor (???).

Conclusions:
- The Brambleberry 12 rectangle is a bad actor. It gives inconsistent results at best, which I can't have in a production operation no matter how small.
- I have no clue what the reason could be; different FO's, lack of FO, CP batch ingredients... but my molds need to be able to handle all normal body rated formulations without discoloring.

 

[penelopejane]

Has that brambleberry mold ever been in the oven over 110*F?
Has it ever been in the dishwasher?
I’m interested because I think silicone is a bit more touchy than we imagine.

Sounds like it could have been a discolouring FO from the past that has contaminated the silicone.

 

[JoeyG]

You might try asking Bramble Berry if those molds are made with Tin or Platinum cure silicone. The library life of Tin cure is substantially less than the Platinum. I believe Tin is something like 1 year, and the Platinum is in the 10-30 Year range, depending on who you ask.

 

[earlene]

Wow, that is great information, JoeyG. Is that a question we need to start asking when we buy silicone molds?

 

[JoeyG]

Wow, that is great information, JoeyG. Is that a question we need to start asking when we buy silicone molds?

Heya Earlene,

I don't think it could hurt to ask. And I would also ask if they're 100% silicone. I've never purchased one of those particular molds, so perhaps they already provide that information on the packaging.

 

[MaryWaldman]

Great questions.

No: they've never been in the dishwasher, and have never been heated above the curing temperature.

They have had several high-quality, body grade FO's (NG, BB, MMS) in them repeatedly since I purchased them. The discoloring problem seems to have started overnight.

Tin or platinum cure? Excellent question, and I will email Brambleberry (their response time has been averaging 7 days). However, the pink 6 rectangle that I use/abuse for testing batches is fine, and the oldest and cheapest mold I own. I think it's selling for $7 on Amazon.

Another interesting point - the blue silicone 12 rectangle molds were purchased May, 2017.

 

[JoeyG]

Great questions.

No: they've never been in the dishwasher, and have never been heated above the curing temperature.

They have had several high-quality, body grade FO's (NG, BB, MMS) in them repeatedly since I purchased them. The discoloring problem seems to have started overnight.

Tin or platinum cure? Excellent question, and I will email Brambleberry (their response time has been averaging 7 days). However, the pink 6 rectangle that I use/abuse for testing batches is fine, and the oldest and cheapest mold I own. I think it's selling for $7 on Amazon.

Another interesting point - the blue silicone 12 rectangle molds were purchased May, 2017.

Just curious, did Bramble Berry ever get back to you?

 

[MaryWaldman]

Hi JoeyG, sorry, I just saw your question.

The resolution was that I mailed the molds back to Brambleberry and they refunded my purchase. I also included the tests you see above. I sent several follow up emails requesting they contact the manufacturer and they dithered - first it was Chinese New Year (a 6 week holiday in China, I believe), and then they weren't getting responses. I never got a resolution to this problem. The soaps and samples I made that discolored on the outside continue to turn brown, but are fine on the inside.