Sciencemadness Discussion Board - chinese 500 ml heating mantle issue

chinese 500 ml heating mantle issue

itsafineday - 3-3-2020 at 09:41

I just bought a 500ml stirring heating mantle from one of the big market sites. My 3 neck 500ml flasks from deschem do not fit the mantle. There is a fairly sizeable gap between the bottom of the flask and the heating mantle . The gap is large enough that when the included stir bar is placed within the mantle, the bottom of the flask does not make contact with the flask. I just returned another unit for the same issue. I also have a 2000 ml mantle of the same general type but my 2000 ml flasks sit happily in contact with the fiberglass mantle.

Have any of you had this same issue? How significant is this issue? Is this a problem with my flasks?

Swinfi2 - 3-3-2020 at 10:42

I had the reverse. My 1000ml flasks fit fine but I bought a cheap Chinese 3 neck and it won't stir because of the huge gap. Sounds like you have an undersized mantle while I had an oversized flask. Wierd as a mantle should be more to spec imo than a handmade piece of glass.

itsafineday - 3-3-2020 at 15:13

Quote: Originally posted by Swinfi2

I had the reverse. My 1000ml flasks fit fine but I bought a cheap Chinese 3 neck and it won't stir because of the huge gap. Sounds like you have an undersized mantle while I had an oversized flask. Wierd as a mantle should be more to spec imo than a handmade piece of glass.

I think my issue is the same as yours and I just wasn't so clear in my description. Fortunately the 500ml mantle still does a good job of heating and stirring. I think I may just be too picky and Deschem has been so good to me in the past I just didn't consider variances in flasks to be the issue. Thanks for responding to my post

SWIM - 3-3-2020 at 19:55

Some mantles are shallower, like Barnstead's table top models.

And some are more flexible, and able to conform to the mantle.

Some Glas-cols are like that, but I'm not sure if the difference is in the model number, or if the floppier ones are just an older, or newer, style for the same sized flask.

Either of these choices might be better for modern glassware from different manufacturers.

These American makers are very expensive, but used they're not too bad.

Also, Barnstead used to sell re-furbished mantles sometimes on Amazon at amazing discounts. $25 to $50 for factory refurbished is pretty good in my book.

SWIM - 3-3-2020 at 19:58

Here are a pair of Glas-cols on Ebay.

They appear to be the same size and are listed as the same model number, but they look like one is shallow and floppy and one is more bird's nest like.

And here's a table top type Barnstead. I'm sure there are other models with these shallower shapes.

[Edited on 4-3-2020 by SWIM]

Sulaiman - 4-3-2020 at 01:50

I suspect that a single-neck flask would fit ok,
some 3-neck flasks get wider just above the halway up level,
is it the flask bulb size, or the necks, that cause the gap ?
If its the necks then you can't blame the mantle

e.g.

SWIM - 4-3-2020 at 12:18

I don't have any, but I've seen a few small mantles made especially for 3 neck flasks which have a non circular top with 2 bulges to fit the flask side necks.

I believe these were for rather small flasks which have bigger bulges proportionately.

Mantle designs are all over the board when you get down to it.
Some are such a close fit you shove the flask in and it won't come back out without real pulling, others are like puffy tortillas and very loose.

And unfortunately, the used ones are mostly sold by people who know nothing about them. Ask some guy selling a used mantle on Ebay about what he's selling and you're lucky if he's even tested it.

I've even seen beaker mantles being sold as hemispherical ones on Ebay, so if you shop for mantles be very careful about inspecting the pictures.

3neckwide.jpg - 4kB

[Edited on 4-3-2020 by SWIM]

Since I was Just complaining about mantle sellers who don't know what they're selling I should point out to anybody who doesn't already know him that DrBob (post below) certainly knows his wares like few people do, and I've never seen anybody regret doing business with him.

[Edited on 5-3-2020 by SWIM]

Dr.Bob - 5-3-2020 at 08:16

The specs for rb flasks are pretty common and similar, and even Chinese made rbfs seem to be pretty consistent. So I would suspect that the mantle is not correct if the flask does not fit. If you have a stir plate, then getting a Glas-col type mantle is ideal, as they are flexible enough to adapt to nearly anything close to a 500. I have even used a 500 ml Glas-col (a floppier one) for up to 1L, and down to 250 or 300 ml flasks. The more rigid ones are not as easy to adapt to much else, other than smaller flasks with sand or other filler to conduct the heat. I still have a few well used 500 ml Glas-col heating mantles for sale, and they are likely almost as cheap as a Chinese one.