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I have an ice cream scoop that is labeled with something like:

Do not immerse in water hotter than 140 °F / 60 °C. Do not wash this item in the dishwasher.

What is the real reason for these warnings? I have found mentions of things like:

  • Hot water will "dry out" the chemicals inside. (What chemicals? Why are they there? How would temperature affect them exactly?)
  • The finish on the scoop may change appearance and may rub off during later use. (Is this due to the hot water? Detergent? Bleach?)

I have a scoop that has accidentally gone through the dishwasher a couple of times without apparent ill effect. Is there now something deficient about my scoop? Is it not being as effective as it was when it was new due to the lack of some mysterious chemicals? Is the finish now coming off into my ice cream even if I can't see it? Is there any health or safety risk due to this?

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What material is the scoop made out of metal, plastic, wood? –  Wayfaring Stranger Aug 6 at 21:47
    
Sorry, it's metal. Probably aluminium. Looks like this but not so shiny (don't recall whether it ever was): gadgets.boingboing.net/filesroot/antifreeze-ice-cream-scoop.jpg –  Greg Hewgill Aug 6 at 21:49

5 Answers 5

up vote 9 down vote accepted

I've accidentally run my scoop, a Zeroll with conductive fluid inside the handle, through the dishwasher. I don't know this for a fact because I didn't cut mine open to check, but I believe what happened to mine (and what's happened to yours) is that the fluid is meant to work at normal body temperature and when it gets too hot, like in a dishwasher, it solidifies. That's the clunking sound, the now-solid conductive liquid. So while it still works as a scoop, the conductive fluid is no longer doing its job and scooping will be a little harder. I definitely noticed that after mine went through the dishwasher.

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Thanks, this seems like the most likely scenario. The seal doesn't seem to have ruptured, and the finish doesn't seem to have been affected much, but it's had this "clunk" sound for some time now and so that's likely what has happened. –  Greg Hewgill Aug 10 at 21:41

Is the liquid inside the handle?

Some ice-cream-scoops are hollow and have a liquid on the inside to help heat conduction - this helps melt the ice-cream and prevent it from freezing to the scoop.

Here's an example:

http://www.amazon.com/Zeroll-1020-Original-Cream-Scoop/dp/B0002U34EW/ref=sr_1_11?s=kitchen&ie=UTF8&qid=1407359424&sr=1-11

Note that it mentions: "Heat conductive fluid inside handle"

If it's filled with a liquid, the extreme heat of the dishwasher might cause it to rupture.

If you have a scoop that's aluminum or stainless-steel and not chrome-plated steel, you're probably fine regarding the finish of the scoop.

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I don't know whether there is actually fluid inside, but when you shake it there's kind of a clunking sound. –  Greg Hewgill Aug 6 at 21:18
3  
Sounds like there's certainly something inside that's helping heat-conduction. I would heed the warnings unless you're OK with it bursting. Keep in mind, they usually overbuild them, and it -probably- will be OK with a run-through of the dishwasher, but you're driving without a seatbelt there. –  john3103 Aug 6 at 21:20
    
+1 for knowing about the hollow handle thing. Good info. I had no idea. –  Carey Gregory Aug 7 at 2:05

One reason could be that dishwasher detergent significantly affects aluminum items. I learned early on that aluminum pans lost their shine and had a dark residue on the surface. Not 100% sure, but it seems like oxidation. With a good cleaning the shine can be restored. However, I no longer put any aluminum items in the dishwasher and no longer deal with this problem.

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Scoop is aluminum, so every day dishwasher treatment could easily cause pitting. Forgetting once in a while and using the dishwasher on it shouldn't be a big deal. –  Wayfaring Stranger Aug 6 at 23:19
    
The black residue is aluminum oxide, the same stuff you'll find on black sandpaper. Bare aluminum oxidizes very easily, but once there's a very thin layer of oxide protecting the aluminum metal from contact with air the oxidization process stops. This is why aluminum looks "dull" instead of shiny. I've read that dishwashers can wash off some of the oxide and deposit it on other dishes (unattractive) and in the guts of the dishwasher (aluminum oxide is an abrasive - NOT what you want in the guts of your dishwasher!). I bought stainless steel pans so I could put 'em through the washer. YMMV. –  Bob Jarvis Aug 7 at 11:00

FOUND IT!

1

From The Sweet Home

The Zeroll isn’t dishwasher safe. Often you’ll see that fact associated with the heat conducting core of the scoop, but that’s not really the culprit. The folks at Zeroll were able to explain a bit to me about how the core of the scoop works, and why it isn’t dishwasher safe.

According to Zeroll, the fluid is a “non-toxic, safe, water-soluble oil”—not antifreeze, as some people suggest. The reason you can’t put it through the dishwasher is actually because of the aluminum body, which is apparently “due to the caustic material in the dish detergent that will oxidize/tarnish the aluminum.

Incidentally, that brand of ice cream scoop won not only the the top rating on that site, but also of Cook's Illustrated/America's Test Kitchen.

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In 1983 I had my 1st job at Braum's in Bartlesville store # 13. They are numbered in the order they were built. Anyway I asked that same question back then and the assistant manager told me they have mercury in them and mercury when heated up sweals . I not to sure how true that is but it could explain the warning though . It's just way dangerous in my opion . Mercury in the smallest amount in our bodies can kill US like super fast . Seems a little crazy to have mercury in it. I recently bought a scooper and asked the manager about it and he said he didn't know what was in there but felt like I did about it that they wouldn't needlessly endanger lives like that. I am curious to that's how I come apon this question that we both have. Will be looking further into it . Will let you know if I find out the big mystery.

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Not sure our store was #13 . I actually think it might have been #19. –  Rhorn Whiteside Nov 24 at 13:34
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Not mercury! See the new answer. –  Jolenealaska Nov 24 at 15:08

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