The_Davster
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My hotplate, she has a problem
I got her slightly over a year ago from cynmar, this one here, but for only 200USD, I think they made a pricing mistake, so I got her really cheap. Now around a month ago, I was drying some
iron oxide in a beaker for about 30min. When I was done I just left the beaker on and turned it off. Well the next day, I pick up the beaker, and
the enamel on the centre of the plate has gone all cracky and is flaking off. I test her out, full heat and everything, no problem, just more
cracking and flaking. So I figure, it's not the end of the world, it is just getting worn. Now, due to finals and then my lab job, I did not have
much time for my lab, until a week or so ago at which point I have an experiment which required the plate. Just making hundred mls or so of a
saturated rubidium chloride solution, nothing too strenous for her. So she is on half heating power, and suddenly, the area in which the enamel had
flaked off gives off this horrible smoke and stench. Now I can guarantee that I did not spill anything on there, I had only used it very rarely in
the last month for mild stirring. I put a pot of cool water on the plate too cool it down and stop the stench, as it is a basement lab, not outdoor.
I figure it is the glues and such decomposing, but how do I fix this? This smell has never come off of it before. I don't really want to buy a new
one, as cynmar has realized their pricing mistake(it would cost 500USD now).
I do have my dumpsterdived hotplate/mag stirrer, but it smells pretty bad when on as well, although not such a 'steam' coming off it. Does anyone
elses hotplate smell bad while in use?
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enhzflep
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All the hotplates we used at Uni and high-school smelled rather ferral if one was lucky. If one was unlucky you grabbed another one or used it next to
the window. Note however that they weren't 1/10 as nice as the one you appear to have and probbably had all matter of evil spilled on them on a daily
basis.
Not that it's much use now, but I'll bet the eneamel cracked off because the Iron oxide retained heat rather well and left you with a rather large
difference in temperature between the center and the outsides of the plate.
I'm guessing that the smell is part of the binder used either in the enamel or applied to the plate before hand to aid in adhesion. Having not been
exposed to atmospheric oxygen whilst being hot it has not been a problem thus far. A possible solution to the issue of odour would be to operate
outside until smell (a)no longer observed or (b) no longer intolerable.
A further possible solution would be to seal the flaking section with high temperature muffler epoxy. As in the kind used to repair holes in car
exhausts. Just operate outside until the epoxy's cooked and ceases to evolve a smell.
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Chris The Great
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I have seen high temperature spray paint. My dad has a can, rated up to 649*C, for use on engines. It even comes in different colours.
I would scrape off the coating that remains completely (including the glue) and recoat with some of that stuff.
The other option is to just burn it all off.
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DeAdFX
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If all else fails their is ebay. I got my hotplate for ~90USD shipped. However the paint idea sounds a lot cheaper. You could also use high temp
RTV Silicone.
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Rosco Bodine
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That ceramic coated steel plate is a weakness on that
particular model from the pictures of the used ones I
have seen bearing the trademark flaking ....it is something that was faulty in the design or manufacture ,
or else it is a vulnerability to a common operating condition which it shouldn't be . A nice way of calling it a piece of shit . This is one of my
pet peaves against
laboratory equipment manufacturers ......they charge a lot for something that is really pretty low tech and could be implemented well , but they
deliver a piece of shit
to you for what you pay good money expecting better .
Instrument quality is a concept which gets dumped in the boardroom for the concept of profit .....and the result is that you get shit for your money .
It is simple cause and effect . The same applies to the stirbars themselves
although they are closer to being right , they are not there yet either , but are an approximation of what
they should be . I have contacted the manufacturers
myself and am sure they know this , and equally sure
that if you want a good instrument you will have to custom build it yourself or pay for it to be custom built
to your specifications . I am presently working on this
very matter , and am considering a limited production
run of instruments that are true instruments and built like
it it in every way , instead of built like cheapass toys
that are pieces of shit from the design stage forward
delivered as a bad joke to laboratories as if the users
there were taken to be non-discriminating morons instead of lab technicians who know instruments from junk .
The motors in the plates I make will be fractional horsepower rated NEMA 48Y frame type HVAC continuous duty ball bearing motors good for 200,000
hours minimum , weighing 4 or 5 kilos each and turning
rare earth block magnet rotors which can couple even through the distance through a mantle case set atop
the stirrer with a switchable rate controller accessory
power jack for alternate use of the heating plate controller as a mantle controller . So not only will
you have a stirrer hotplate , but a base unit for
a stirrer heating mantle . No more bullshit from
the equipment manufacturers ....no more waiting
for something built right to do the job of heating and
stirring open vessels or mantle applications .
I pretty well expect to lose money in the endeavor ,
but it has become something of a grudge for me
that needs settling , for years of trying to get some
better equipment from the mass producers who are
fully dedicated to selling only shit while fraudulently
advertising it to be engineering .
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The_Davster
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Yeah, sometime in the near future I will spending some time with the power sander, just get it down to all steel.
Chris would you mind spraying some of the paint on steel, and then heat it up alot, If the paint stinks, I am right back where I started.
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Rosco Bodine
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It is almost certainly non-magnetic stainless steel ,
so why paint it with anything ? Just sand it smooth
and leave it naked . In fact some of the manufacturers
supply them with or without the ceramic coating .
A white surface simply provides better visualization
of color changes . You can probably disassemble the
unit and remove the steel pan to get to it better for
cleaning , probably heating it up good with a torch
and then splashing cold water onto it will shatter and flake off all of the ceramic coating right down to the metal .
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The_Davster
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Ah, thanks for the clarification Rosco, when you said steel in your first post I assumed non stainless.
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Rosco Bodine
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BTW , here is 7 more of 'em for $90 US apiece in
quantities of 1 at a time , good condition used equipment .
http://www.surpluslab.com/detail.cfm?autonumber=55071
[Edited on 20-6-2006 by Rosco Bodine]
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The_Davster
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Well today I finally got around to fixing her up. Made a nice roaring fire, and tossed the plate in(removed from the rest of the hotplate of course)
and then took out and crashed into a bucket of water. This was repeated untill the bucket of water was almost boiling. Most of the enamel came off,
a few spots on the very side are left, but I doubt the heat will effect those areas much. I tried to polish it up with the power sander, but the
little lower enamel left is really tough stuff, it did not do anything. Oh well, I reassembled her, and she looks but-ugly now as much of the enamel
undercoating is left, but works fine without stinkyness. I might try to make her pretty eventually, but she is fine for now.
EDIT: forgot to mention, now when on high heat the plate has a distinct convex rise on top. That could have been a stresser on the enamel causing it
to crack in the first place. I may end up just looking for a machine shop somehwere and asking for a new stainless plate for the hotplate made
exactly like that last.
[Edited on 22-8-2006 by rogue chemist]
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Texium
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Thread Moved
19-11-2023 at 11:19 |
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