Sciencemadness Discussion Board - Chinese Hotplate/Stirrers

Chinese Hotplate/Stirrers

highpower48 - 29-12-2016 at 15:46

Has anyone tried the $100.00 Chinese Hotplate/Stirrers? Are they worth the price?

Corrosive Joeseph - 29-12-2016 at 15:50

Maybe a link or two might be handy..........................?

/CJ

highpower48 - 29-12-2016 at 17:27

Will do so when I get home. Phone app does not give me a url.

JJay - 29-12-2016 at 18:26

If it's the 85-2 stirrer, I wouldn't recommend it for chemistry, although it's not so bad if you just want to stir a fermentation mixture, work with ether, or keep an electrolytic cell at a certain temperature. I could see it as being useful to brewers or perhaps in medical or bio laboratories. If it had a ceramic top, a more powerful heating element, and better documentation, as well as a thermostat that goes to 350 C, I could see it as being a lot more useful. There are a lot of things I like about it, but I just can't recommend a hotplate that won't boil water to chemists.

I haven't tried the 85-2A stirrer, but I am curious about it.

highpower48 - 29-12-2016 at 18:34

Look at this on eBay http://www.ebay.com/itm/232092408590

JJay - 29-12-2016 at 18:45

It's only 180 watts... that's really not very powerful.

I'd just get a used Corning PC-351 or PC-320 (or something similar).

Geocachmaster - 29-12-2016 at 21:21

Quote: Originally posted by JJay

It's only 180 watts... that's really not very powerful.

I'd just get a used Corning PC-351 or PC-320 (or something similar).

I think this is a great idea. I ordered a used Corning PC-351 on Monday and it arrived today! I got it along with 8 stir bars for ~$120, so it's not that much more expensive. I've tested it a bit and I love it already. Worth every penny

diddi - 30-12-2016 at 03:38

the chinese one I bought had a nice digital readout and looked great. when I used it the first time, it literally melted and nearly caused a fire. lucky I was checking on it regularly. now I have a good one tf and it works perfectly every time. and not a chinese brand either

PirateDocBrown - 30-12-2016 at 09:39

I got one under the tree this Christmas. Haven't tried it out yet.

PirateDocBrown - 31-1-2017 at 23:50

Seems to heat OK, but at 180 watts, it's gonna struggle to boil even a liter beaker of water. The stirrer is fine. It came with a stirbar, too.

The thermometer stand is useful.

Nothing at all wrong with it, it's just small.

How long it lasts, only time can tell.

[Edited on 2/1/17 by PirateDocBrown]

Melgar - 1-2-2017 at 13:29

It's probably designed for 220 volt systems, and made for the rest of the world aside from the US, Canada, and Japan. Since P = VI and V = IR, then P = (V^2)/R. When you divide V by 2, that divides power by 4, and multiplying V by 2 multiplies power by 4. So a 180 watt resistive heating element at 110 would output 750 watts at 220, a much more reasonable number.

However, these could also be ones that didn't pass quality assurance for the heating element, but would be okay to run at half the voltage they were initially supposed to run at. So if money is tight for you, don't go looking for ways to boost the AC voltage or anything.

I actually used this to my advantage when building a still in college. You needed to first heat up room temperature water to boiling, then collect it from the top. At 1000 watts, it took FOREVER to boil, so I bought a 220 volt, 4000 watt hot water tank heating element. I'd plug it into the dryer outlet (220 volts) until it was boiling, then switch to a 110 outlet for collecting. It'd be easy to get one now, but it was hard to find 220 volt TRIACs back then.

18thTimeLucky - 21-8-2017 at 23:54

I thought I would invest in a hotplate stirrer as it is starting to be painful to not have one; a spirit burner can only do so much.
As this will be my first hotplate/stirrer and I am poor as crap, I was wondering if any of you beautiful people could recommend me cheap hotplate stirrers that are still quality enough to heat sufficently and not break within the first 30 seconds.
£100 is my maximum budget really but maybe this is unreasonable and I will have to accept the fact that I will only have some dirt and the hotplate stirrer to my name after purchasing it.
I had looked into the 85-2 and the SH-2 as they were the cheapest on eBay (within £40-£60) and are sold by multiple sellers. It was interesting to read on this thread they are probably not worth the money anyways. The SH-2 says it can manage a maximum temperature of 380^oC although what I have understood is despite that, being 180 Watts it would take a million years to heat up?

http://www.ebay.co.uk/itm/1000ML-Magnetic-Stirrer-Mixer-Mach...

http://www.ebay.co.uk/itm/Magnetic-Stirrer-With-Hot-Plate-He...

Would it be worth to bite the bullet and buy a more expensive second-hand hotplate from a good quality brand name?

Any answers would be appreciated!

Melgar - 22-8-2017 at 00:06

If you have more time than money, you can build one from the base of an electric kettle. I hear those are quite popular in localities where pounds are a unit of currency. Hair dryer fan motors are excellent for stirring too, you just need to mount a permanent magnet to the shaft and figure out how to control it.

18thTimeLucky - 23-8-2017 at 01:25

That is actually a very good idea, I had not really considered making one. I am not fantastic with electronics but I have a friend who is so maybe he can lend me a hand.
Hotplates without stirrers seem to be quite cheap, I found a 1500W for £20, so I might purchase a hotplate and build a stirrer; I heard computer fans can do the job quite well too when building a stirrer.

Reboot - 23-8-2017 at 16:00

Hello!

In my experience the way these thing usually work out is that you tinker, play, and end up not really saving much money for what turns out to be an inferior product. The process is interesting, it's fun, it's educational. On the other hand, if you really just want a decent, reliable hotplate-stirrer, you're probably better off saving up and buying something ready-made.

I'm not sure how things are on your side of the pond, but here in the states, the going rate for a good used (modern, in decent shape, quality brand) hotplate-stirrer is around £150.

For me the big 'quality' indicator is heating power. I look for something around the 500-700W range, which is enough for small-scale heat-hungry distillations. If it has that kind of power, the stirrer is probably well-built too.

Electronic controls and displays raise the price, of course. I feel a temperature setting readout and an option for a temperature probe is worth getting, but your milage may vary. Personally I don't see any real value in an RPM readout (usually 'as fast as it goes without destabilizing the stir bar' is the right setting for me. :-)

I like physical knobs. Up/down buttons to (for instance) change temp settings are easy to manufacture, but they seem awkward to me.

18thTimeLucky - 24-8-2017 at 02:58

I think it would be a fun project to make a stirrer anyways but I will take it from your experience that this is not necessarily the best route in my situation.
I am by far not a experienced amateur chemist so I am not familiar with hotplate stirrer prices, even here in the UK, but I considered your advice of a 500-700W range and I found a few reasonably priced products on eBay and I was wondering if I could have an opinion on them. The page and the whole specifications can be found by the links and they seem to be trustworthy sellers. Thank you!!!

http://www.ebay.co.uk/itm/SH-3-Hotplate-Stirrer-17x17cm-Anod...
£86.88
SH-3 hotplate stirrer: 500W: 220V: maximum 380^oC: 100-2000RPM: stirring capacity 3L: no warranty

http://www.ebay.co.uk/itm/HOTPLATE-STIRRER-STIR-HEATER-MIXER...
£119.99
GLTlab hotplate stirrer: 500W: 220/240V: maximum 450^oC: 50-2500RPM: stirring capacity 10L: 2 year warranty

http://www.ebay.co.uk/itm/220V-Hotplate-Magnetic-Stirrer-SH-...
£145.00
SH-4 hotplate stirrer: 600W: 220V: maximum 380^oC: 100-2000RPM: stirring capacity 5L: 1 year warranty

Σldritch - 24-8-2017 at 05:00

I just bought the last one (SH-4 ceramic). Trying to distill a liter of water right now in a sand bath but it does not seem to work. I think these hotplates are pretty pathetic heating wise but that is not much of a problem if you have a burner too.
Ill try without the sand bath and update.

If you are in US i think an used corning hotplate stirrer would be better.

18thTimeLucky - 24-8-2017 at 06:42

I would be very interested to know how that goes for you. Please do provide an update! That is unfortunate if you find it to not be heating properly; hopefully you can speak to the seller and get a refund if this is the case. If not at least we can be pretty confident in not trusting that seller or brand in the future. It does have a 1 year warranty though.
Lets hope it was just the sand bath that was being slow.
Buying hotplate stirrers seems to be a needlessly tricky business!

[Edited on 24-8-2017 by 18thTimeLucky?]

Reboot - 25-8-2017 at 16:51

Quote: Originally posted by 18thTimeLucky?

http://www.ebay.co.uk/itm/SH-3-Hotplate-Stirrer-17x17cm-Anod...
£86.88

I would avoid this one. The (inexpensive) aluminum surface will be pretty vulnerable to corrosion from chemicals. Since it's not a 'proper' material for a chem lab, it makes me wonder how well-made the rest of it is.

Quote:

http://www.ebay.co.uk/itm/HOTPLATE-STIRRER-STIR-HEATER-MIXER...
£119.99
GLTlab hotplate stirrer: 500W: 220/240V: maximum 450^oC: 50-2500RPM: stirring capacity 10L: 2 year warranty

Looks like a very basic, even primitive design, but a ceramic top (or stainless) is appropriate and I like the weight of the unit. (Physically light hardware tends to be an indicator of low quality when it comes to these things.) Probably a solid contender.

Quote:

http://www.ebay.co.uk/itm/220V-Hotplate-Magnetic-Stirrer-SH-...
£145.00
SH-4 hotplate stirrer: 600W: 220V: maximum 380^oC: 100-2000RPM: stirring capacity 5L: 1 year warranty

I would lean towards this one of these three. The case is clearly more expensively manufactured than the previous unit (a casting instead of bent sheet metal), which tends to be a good quality indicator. The built in rod holder is a small detail but it can be a handy convenience (even with a flat bottom flask an assemblage of glassware can get quite tippy!)

Mush - 26-8-2017 at 08:37

SH-2 model does the job surprisingly well. It's adequate to small volumes about 100-200 mls. Larger than that one would need a bit more powerful hotplate.On maximum power , 150 °C can be reached (in the reaction flask) with 500 ml oil bath in a pyrex dish. Excellent for home usage even for school labs. For very pro use go for something else. I would say price /value is 7/10. After 7 month, 6-7 h a day use, still works.

[Edited on 26-8-2017 by Mush]

18thTimeLucky - 26-8-2017 at 10:18

I'm so confused what hotplate stirrer to buy! I don't know whether to make one, buy a cheaper one, or go for a moderately priced one. I am by no means unthankful; I really appreciate all the help!
I might think about going for the SH-3 model. Mush, you said from experience(?) the SH-2 is excellent for most small scale reactions, and Reboot, you said the SH-4 seems to have good quality indicators so although you said the SH-3 has got lower quality indicators it is a similar model (SH) and my poor wallet can only dream of owning even the SH-4. When I have more money in the future and my cheapo hotplate stirrer kicks in I can afford a more expensive, higher quality hotplate stirrer.
I will think about the GLTlab hotplate stirrer as it does seem a solid contender as you said (also I love the 2 year warranty). I hope Σldritch gives us a update about the SH-4 as that will help make a decision whether the SH series is potentially good quality.

Again thanks so much for all the help, I have only been an amateur since December last year and I am studying chemistry at A-level and in a year at university and I wish I had found this gold mine of a forum sooner! I look forward to contributing and helping others too when I have the opportunity!

Σldritch - 27-8-2017 at 02:46

Late update: i tried distilling water with my SH-4 by just thoughing the 1 liter RBF to the hotplate. It does distill then and i could probably increase the temprature it can distill at by adding some sand around the RBF. The stirring works great unless you have some metal between like a steel pot.

I wouald have bought a used corning but in the EU i could not find anything this cheap. It might not be the best (it really isnt) but with a burner i think it works; you are not going to use a magnetic stirrer anyway at around 300C.

So i guess i recommend it if you are looking for something really cheap which was also the reason i bought it. If you can find anything better in the same price range it is probably better but used cornings and such hard to come by in the EU. Also there is a one year warranty which is reassuring.

[Edited on 27-8-2017 by Σldritch]

Melgar - 28-8-2017 at 20:20

Quote: Originally posted by Reboot

I used to think that too, until I realized that it takes a ridiculous amount of time for acid to dissolve through aluminum that thick. Try putting a piece of aluminum wire in straight HCl and time how long it takes to dissolve. I bet it's longer than you expect.

There's actually an element of safety built into using aluminum as well, believe it or not, since if you're not paying attention, and a vessel overflows, you can hear it immediately.

I can't tell you how many times I spilled corrosive chemicals on the surface of my last hotplate, which was aluminum. But after all those years of abuse, the deepest anything ever ate into it was only about 1 mm.

If you want to build a hotplate, make sure to get something with a circular heating element, so you can put the stirrer magnet in the middle of that. Also, go beat the piss out of whoever told you that computer fans make good stirrer motors. They're MUCH too weak. However, if you take apart an old printer, you'll probably find at least three DC motors that could do the job.

SWIM - 4-9-2017 at 23:45

There are some hotplate stirrers on the market that are even cheaper than the sh-2, but are rated at 300 Watts.
The Bipee 78-1 can be had on Amazon for $74!
Why so cheap? the stirrers has a speed control, but the heating element is an on/off situation with no rheostat.

I don't know how reliable Bipee products are, but it should be a breeze to wire an external dimmer switch to the part of the circuit that powers the heating element. There's a separate on/off switch for the heating element that you could replace with a jack to plug in a rheostat.

Then you'd have some extra wattage, a stainless steel heating surface, and decent power control for less than $85.

And If you ever burned out the rheostat you wouldn't have to worry about finding a replacement that fits in the casing.
Just go to your local hardware store for another cheap dimmer switch.

18thTimeLucky - 7-1-2018 at 04:55

It has been a few months now so I thought I would return to this topic in case anybody finds themselves in a similar situation.

I ended up buying the hotplate stirrer from this link from eBay:
https://www.ebay.co.uk/itm/HOTPLATE-STIRRER-STIR-HEATER-MIXE...
Since I mentioned it before the price has dropped by £10 to £110. I ended up buying it when it was £120 but payed £110 anyways due to an offer I made to the seller.

The only thing I can really complain about the hotplate stirrer is that the specification was off when comparing what I received to the sellers page. For instance, the heating power is said to be 500W but in fact what I received had written in the instructions manual that it was 400W, and a few other things like that.

Other than that though the stirring function worked great, I have never needed to turn it up higher than half way to full power. The heating works fine too, it can easily get above the boiling point of water and seems really fast with volumes around 200ml. I do not know how hot it can get, but I have so far never needed to continually use the full powdered heating. The product also arrived very quickly - within a few days if I remember correctly.

I have not really stressed it, just used it for things like distillation of propan-2-ol, evaporating water from a sodium ethanoate solution, general stirring etc.

On top of the two year warranty I would thoroughly recommend this as a hotplate stirrer though if you are looking for something new, cheap and functional.

semiconductive - 8-1-2018 at 07:13

Quote: Originally posted by JJay

If it's the 85-2 stirrer, I wouldn't recommend it for chemistry, although it's not so bad if you just want to stir a fermentation mixture, work with ether, or keep an electrolytic cell at a certain temperature. I could see it as being useful to brewers or perhaps in medical or bio laboratories. If it had a ceramic top, a more powerful heating element, and better documentation, as well as a thermostat that goes to 350 C, I could see it as being a lot more useful. There are a lot of things I like about it, but I just can't recommend a hotplate that won't boil water to chemists.

I haven't tried the 85-2A stirrer, but I am curious about it.

I second this opinion. I bought the 85-2, and converted it to run on 110VAC instead of 220VAC by installing an American doorbell transformer in it. But the controller only goes to 99.9C ... I bought the system for it's mechanical box and magnets, because I had the intention of getting rid of the built in controller and replacing it with a circuit board to run it using my own TI MSP430 temerature board that is meant for running kilns up to 1100C. It can also be controlled by a raspberry pi. But for Chemists looking for an out of the box solution, these stirrers don't allow setpoints high enough and don't get hot enough at 110Volts. If you plug them in to 220VAC, (Dryer outlets), they can INDEED get hot enough.

As a note, the controller *IS* able to boil water. It's just not able to set the temperature boiling point above 99.8C before becoming open loop. (Their controller looses temperature regulation when set to 99.9C and it will often spike up to 150C at 110VAC wall voltage.).

The rubber temperature probe holder is also not very useful as it can't hold the thermometer firmly. Which is why I welded a metal plate on the end of the holding rod, so that I could use a u-bolt on the thermometer -- or to hold a glass vial/test tube instead. I also removed the thermometer from the stainless steel jacket because the metal sleeve is actually more reactive with acids than the plastic cord is. ( besides, the jacket makes temperature measurement slow. )

Not having a ceramic top isn't very important ... as stainless steel can be covered with aluminum foil or a glass/sand mixture which can be thrown away. Even more expensive controllers made in the USA with ceramic tops get ruined by chemicals. Check out second hand American hotplate stirrers on ebay, and look at the tops. They are generally in bad shape. No matter what you buy, you'll almost certainly ruin the finish on it if you use it regularly. Besides, stainless steel can be sanded with fine grit sandpaper and you will get a clean finish again just patinaed. It doesn't look bad after cleaning up like ceramic does.

I'm refluxing H2O2 with my stirrer plate, right now. I'm doing it to condensing 3% store bought peroxide into 10 to 30% strength peroxide. Today's the last day of Christmass (day 12) and with help from St. Nick's hat, the water will boil just fine in an hour or so. (I'll upload second picture with hat later. ) You might wonder if it's a Christmas miracle that water steams and boils at 95.5Celsius when I'm only 75ft above sea level ... until you notice where the electronic thermometer is. It's the black cord at the top of the Vigereux column.

Still, the 85-2 is a very low cost stirrer frame for me to build a good system in using my electronics know how. I'll likely show my modified version sometime this coming summer.
The main points I plan to upgrade are 1) the thermometer needs to be chemically passivated with glass, 2) the motor needs a speed controller so that it doesn't stall when stirring very slowly 3) The temperature controller needs a much wider range and 4 digit LED display instead of three digit.

[Edited on 8-1-2018 by semiconductive]