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Transparent soap and purple chunks
Dear colleagues,My customer has began to manufacture the clear soap. The formulation is great. But, the huge purple chunks on the bottom of the stainless steel tank are found everytime after making every single batch. I have never run into this effect formulating many formulations of the transparent soaps. My question is what is this? I do appreciate any of your thoughts regarding this problem. Thanks in advance.
The formulation contains: Propylene glycol, Glycerine, Sorbitol (powder version), Stearic acid, Myristic acid, Lauric acid, NaOH, EDTA, BHT, TEA, Water and SLES (70% paste).
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12 Replies
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Have you tried passivating the tank after a very complete cleaning?
Also, do you see the same problem with making the formula in a glass beaker?
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First of all, thank you for your thought, Bob. Unfortunately, I have not seen their tank. I have only formulated the product, but I recommended to passivate the tank to avoid the occurence of possible complexes or to order another special tank for this product. I didn’t run into such strong discoloration during the formulating process beside the yellowing, but this problem had been solved completely with introducing of Trilon M.
So, Do you think those purple conglomerates aee the result of complexes with EDTA ( tetra sodium)? Would it be the recation with some trace impurities or byproducts of TEA or SLES? Please, advise.
Again, Thank you. -
This is fascinating. Manganese getting leeched out of the steel, maybe? Either way, beautiful color, though probably not safe for use.
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Sunstone, manganese? That’s still unclear whats going on, since this reaction is visible both in their tank and in the laboratory glass beaker. There is only difference - they get the pieces of the pink soap in the tank and just a pink color in the beaker. When I’m doing that in my laboratory the soap is completely clear with no pink tinge. I suppose the reaction occur due TEA or some impurities in the ingredients they use in the presence of chelating agents in the system.
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Are they actually using the same raw materials or just go one for one on the INCI?
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@BartJ , They have got their own ingredients. The technical data are identical to mine ones. However, they get the results like this.
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The first thing to try with this problem is for you to prepare samples in your facility using ingredients which are known to be causing the problem i.e from your customer. Depending on the outcome of this you will be able to determine the source of the colour - ingredients or processing conditions.
You might also try omitting the BHT (phenols notoriously give colour reactions in the presence of iron showing a pink or purple shade).
When I was involved with the manufacture of bar soaps, BHT was a definite no-no as, even without the presence of metals, it discoloured to a very bright yellow. Nice if you wanted yellow soap but not of much general use.
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Thank you so much, Johnb for your expert input. I have ommited BHT and advised to use a trace % of Sodium Metabisulfite and it solved the problem completely. The result is waterlike colorless soap.
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Mixing tank better should be 316 L type but most important change the source of PG. Any kind of Fe in PG can cause it. I have live such problem with BASF PG even Fe contant under spects but did not live PG from Korea . EDTA or HEDP could not solve the problem.
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You can try sugar instead of PG in your formulation.
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hasanarsan
Please be aware that this query was solved in September 2016. There is little point in you reopening the discussion. -
hasanarsan, Thank you for your input, but sugar renders yellow tint to the soap at high temperatures.
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