Monday, February 21, 2011

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What is that White Film on My Silicone Ice Trays?

Talk to enough cocktail types and eventually the name Tovolo comes up. Not, it’s not the name of a pre-Prohibition bartending genius or an obscure Italian amaro. Tovolo is the international housewares division of ICI USA and it makes, among other things, a nifty silicone ice cube tray that makes dense cubes — actual cubes with equal sides — of ice.

Talk to enough people who use those trays, though, and a common complaint arises. After some time in the freezer, the trays may develop a persistent white surface film.

 The film forms on the interior and exterior surfaces of the trays, is transferred to the ice, and gives an off taste and smell to drinks as the ice melts. There’s even a waxy residue on my tongue after getting Tovolo ice cubes from trays that have the film.

What the hell is this stuff? And how to you get rid of it?

It doesn’t seem to be caused by mineral-heavy hard water (otherwise, we’d likely see it only on the side of the trays, but see below for a contrary finding). It seems, rather, to be some reaction of the silicone itself. One thing that makes me think this is that of all my kitchen utensils, the silicone spatulas — and only the silicone spatulas — develop a different, almost greasy feeling, surface coating. Now, I do keep those next to the stove, so perhaps they attract minute particles of airborne cooking grease that the wooden and metal utensils don’t. When I expand my consideration to kitchen gear more broadly, the Silpat silicone baking sheets acquire that same slightly greasy feel if I haven’t used them some time and I keep those in a closet away from the stove. Both of those films wash off easily with a soap and hot water.

This is not the same film the ice cube trays develop; that all of my silicone eventually behaves oddly is the only connection I’m making. I’m not a chemist and don’t know what’s going on.

So I threw out a question to members of the Cocktail and Spirits Online Writing Group: anyone else notice off-tastes from these cubes and, more to the point, have luck restoring these trays?

Yes, writers noticed the film as well. Not everyone, but several had. There was no consensus on what caused it. Suggestions for restoring the trays ranged from using toilet bowl cleaner (um, pass) and boiling the trays in water to scrubbing them with vodka or vinegar and running them in the dishwasher.

I have tried all those suggestions (well, not the toilet bowl cleaner) and am here to tell you that none of them works. At least, not for very long.

Soaking and rubbing the silicone ice cube trays with vinegar and vodka (separately) initially eradicated all traces of the white film, but it bloomed on each test tray again within a week. I boiled a tray for five minute: no dice. Ten. Same. A twenty-minute boil did nothing to remove or reduce this persistent film.

Finally, I wrote to cookware doyenne Mariella Esposito of Fante’s kitchen supply shop in Philadelphia. She got in touch with a silicone tray manufacturer who wrote this:
We have heard this type of feedback before on the ice trays and have tested them extensively. We test both the original raw material, the catalyst, as well as samples of trays that have been used and been returned to us by customers.

We actually did a chemical breakdown test on this white residue from a tray that we rec’d back from a customer and the result of that test is below. The compound associated with the residue is Calcium Sulfate – meaning basically the residue is associated with the chemicals in hard water. Like a mineral deposit. The minerals from the water calcify and adhere to the walls of the silicone and are then transferred to the surface of the next ice cube to be made.. etc.. etc.. etc..

We have found a dilute solution of vinegar and water to be a great solution. Simply soak the trays in this for about 20 minutes, rinse them and you should be ready to go. Most soap based cleaners can also leave trace amounts of milky residue on the ice trays. You ‘ve seen those old dishwasher detergent commercials where they take the glass out of the washer and it has a white residue on it… viola.
So, there you go. A suggestion that calcium sulfate is at play on at least one tray tested and may be cleaned with vinegar. My guess is that probably does work with some trays. But not mine.

Any chemists out there have recommendations on what else this stuff may be and how to eradicate it?

Otherwise, I’m left with the words of Nathan Lutchansky, a cocktail enthusiast in Pittsburgh:
Yeah, that happens after a while with those Tovolo trays. At that point they're worn out enough that we just throw 'em out and buy new ones. They're pretty cheap.

Goes well with:
  • Tovolo sells their trays on Amazon. Despite my questions and frustrations, I do still like their trays. You can find some of their selection here.
  • If you'd like to reach out to members of the Cocktail and Spirits Online Writing Group yourself, check out the group's website here and drop in the Mixoloseum chat room on Thursdays for themed nights of drinking, mutual heckling, and frequent visits by brand reps, authors, bartenders, and distillers.
  • Fante's Kitchen Wares Shop, one of my all-time favorite cookery stores in the entire United States — and, yes, that's exactly the sort of place I visit when traveling. A sprawling warren of rooms filled with knives, copper pans, mixers, juicers, pepper mills, cake pans, bread baskets, pickle grabbers, meat mallets, food coloring gels, and, yes, ice cube trays.


Mike said...

Makes sense, sort of. I've never had this problem, but I only use mine for freezing chicken stock.

Tony Harion said...

I switched to the cocktail kingdom ones and haven’t had the problem so far.
The CK ones are a bit harder to get the ice out, but work well for me.

have you ever used them?

frederic said...

Our oldest trays look as good as our newest ones (two year span of samples), but then again, we do not have hard water.

I did read somewhere that someone had success avoiding the white film by using low mineral bottled water for filling the trays.

And Tony, did Cocktail Kingdom solve the problem of floppy/flimsy trays (hard to fill and carry because they are not as rigid as the Tovolo ones)?

Michael Lazar said...

I ditched mine a long time ago for precisely this reason---and I could never clean them, just as you found. The ice was always kind if foul. I am fortunate enough now to be living in a rental house now w/ a very decent ice maker so I am spared the whole tray ordeal.

- Michael

Tony Harion said...


My cocktail kingdom trays are from the early batches of trays they made so they are floppy.
I don’t know if they solved that. It only bothers me to remove the ice and not so much to carry them around.

Matthew Rowley said...

Mike ~ I always liked the idea of freezing chicken stock in ice trays, but I realized that I almost never use that small amount of stock. Perhaps I should try — if I ever get these things clean.

Frederic and Tony ~ thanks for the heads up on the Cocktail Kingdom molds. Will check them out.

Michael ~ Am envious. We still either use molds or trim 'em by hand...Unlike certain Traders Tiki who have Kold Draft machines in their homes...

Janice said...

Interesting, I have the Tovolo perfect cube trays, and have been using them for , but mine are red, and no sign of the offending film.

Matthew Rowley said...

It's odd, Janice ~ some trays get the film, some don't, even using the same water source. I didn't get red trays because, as a childhood redhead, I can't abide the color around me to this day. Perhaps if I had overcome childhood prejudices and bought red trays rather than blue I never would have noticed...

Nick said...

I have this problem too, although I thought the off-tasting ice was because the silicone was holding on to the smells from my freezer. When I first take the Tovolo trays out of the freezer, they smell unpleasant, but if I let them air out for a few days the smell goes away.

I do have hard water, and also was never able to get that white film to totally disappear. For me, the film appeared basically from right when I got them, so I just don't use them much and wouldn't want to buy more.

Matthew Rowley said...

Nick ~

I think what we're seeing is a combination of factors that create similar seeming, but chemically different, reactions. My trays also got a funky smell at one point that went away — I had stored them next to several pounds of andouille sausage from LaPlace, Louisiana. First, I cleaned the trays thoroughly, aired them out, then sealed the andouille better. Of course, the ultimate solution to that problem was making a few gallons of gumbo and a several pots of red beans.

Glad to hear from you and hope you find some useful things in these pages.


Anonymous said...

It's odd all the hard water talk, but when I use distilled I get same problem. Ive never soaped the trays and have done multi pull fills in same tray with distilled after cleaning tray in distilled water. Same results I personally think the trays leach something because the water sure isn't. An interesting experiment would be to fill cup over and over with this ice letting it evaporate each time till a very large amount of this waxy residue appears and have it tested. Using distilled water from the get go of course. New tray also at the start.

Anonymous said...

So to summarize from many websites: it happens with all types of water. I soaked mine overnight in weak acetic acid (white vinegar), weak phosphoric acid (coke) and weak citric acid (mountain dew). Likewise, mine are so new that I havent washed them using soap of any kind. I can scrape this gunk off, but am not intending to got to the expense of having it tested. Also baffling is a post that stated it only happens to the blue-hued ice cube trays, but not the red. I give up.

Anonymous said...

I have the same problem and found this blog. i'll try the vinegar and if it doesn't work - out they go. I am testing a cube right now and see the residue floating in my quadruple filtered water (both the cubes and the water sample). I have only tried to wash this in the dashwasher a few times to no avail.

Anonymous said...

I have been using the blue ice trays for six months now and cant figure out how to get rid of the white residue. I'm pretty sure its something leaching from the tray. What I do is wash the cubes under water before use. Not real practical, but it works. I've given up washing as it doesn't remove whatever it is. Ill be switching trays soon.

Anonymous said...

I have the red trays and I do also get this white film. It's not so bad that I don't use them, but I do notice it. Although I only use the cubes for mixed drinks so have never noticed an off taste. I have noticed it leaves an oily residue on the tops of drinks occasionally.

L Dubs said...

I have the nasty taste problem but no hard water film. I read to let the trays sit in a water backing soda mixture for up to 3 days and change the water every day. I am in the process of trying that.

Good luck!

Barbara BTazbin said...

I have read that the baking soda in water soak works the best. I have the green trays, and the ice cubes smell and taste awful. Trying the vinegar in warm water soak, first. Then will try the baking soda and water if that doesn't work. I read that you really have to put a high concentration of bs in the water, to the point where some of it settles to the bottom undissoved. Ice cube trays should not have to be a high mainenance item!

Matthew Rowley said...

I agree completely: ice trays and molds ought not be high-maintenance objects. I've used others for freezing lobster butter and had no lingering odor at all (surprised me). All the solvents and cleaning solutions are more appropriate for heirloom linens than a simple kitchen tool.

Gary said...

My ice cube trays have the same problem, but even when I rinse my ice cubes to melt away the entire outside layers....they still taste awful! I also have only filled them with filtered water. So that negates the Calcium Sulfate theory. Mine are blue.

Anonymous said...

Stopped storing cubes in the tray and put them in airtight freezer bags right after freezing. This seems to have helped with the rubbery taste from the cubes. Will keep testing. My black tray has never had residue on it.

Anonymous said...

I have this problem on my new dark purple trays. I ran them in the dishwasher when I first brought them home. Top rack just like the sticker said. That is when the film appeared. I thought it was dishwasher residue.
The film stays on the trays after vinegar rinsing and after I rinsed them with Dawn. I can wipe each tray out with a towel and get the white film off. I froze some water in them and dumped out the ice hoping it would pull the film out too. Nope.
I have never used these trays and will never buy another set!!!

Anonymous said...

I had a rubber iceman shape ice cube trays, when I put the ice cube in a clean glass of water, the ice cube would start melting and fill the glass with floaties from the film residue on the tray, wth man, wth

Unknown said...

We're only frustrated by this because we love the trays and resulting cubes so much. Ours are Tovolu dark purple. The residue shows up on the trays and in our glasses and in the drink. It's good to know it's nontoxic (at least in someone's opinion). Someone recommended rinsing the cubes before dropping in the drink.

Anonymous said...

Could it be pthalates leaking from the silicone?

Anonymous said...

The residue on the ice from my red Tovolo 1" cube trays seems to be caused by the freezing process itself. I've tried all of the suggested cleaning methods, as well as filtered (not distilled) water. I have the two inch trays, in blue, as well and do not have the same issue with them. The interesting thing is that the film and residue take on a similar shape as that of ice crystals. I can't say that I've ever got an off taste, though.
Whatever the cause, (however strangely fascinating) I'm done with this experiment and they are getting tossed.

Matthew Rowley said...

Tossing them was my eventual solution, too. I understand the argument that the trays aren't very expensive and replacing them is easy, but — and perhaps this is California wearing off on me — I'm not wild about simply throwing out plastics because they get off-tastes. The better plan for me is not to use the trays and if I want big clumps of ice, I'll form them by hand. They may not be perfect cubes, but they'll do they job without getting filmy.

Anonymous said...

I have the green ones and have the same problem. I have tried all of the above, using only Pur filtered water, but it keeps coming back. I'm not too keen on ingesting something that looks like tiny slivers of plastic, so out they are going. I have made my ice cubes the same way, with the same filtration system, using various ice cube trays, & yet these are the only ones that have this residue. I don't think they are cheap, either. I got them at a kitchen store & spent $8.00 for four of them. Now they are in the garbage after only five months. Pretty much just threw $8.00 in the trash. I think we all got duped.

Holly Bowan said...

I googled this question because I have the same problem with my silicone muffin tray. I'll try the vinegar.