Heated water baths?

[ffutures]

My school needs some more thermostatically controlled water baths - temperature range from room temperature to say 80 degrees Celsius, capacity at least 8 litres, capable of maintaining temperature for two or three days without going wildly wrong. They are VERY expensive from laboratory suppliers, e.g. £200 plus, but lab suppliers tend to have inflated prices.

Are there any alternative uses for this sort of thing I'm missing, where there might be cheaper water baths available? About the only thing I've come up with so far is yogurt makers, but they have a fixed temperature. Also aquarium heaters, but the temperature adjustment tends to be a fairly narrow range. Any other suggestions?

Comments

[cdybedahl.livejournal.com]

Stuff for sous vide cooking should fit your requirements, but may be even more expensive.

[karohemd.livejournal.com]

Indeed and the capacity is far lower. I recently had a look just for the hell of it and came out wibbling...

[fhtagn.livejournal.com]

Well, I know that cairmen hacked together a water-bath for his sous-vid experiments from a slow-cooker and a £5^[1] feedback circuit from somewhere and seems to be having success with it. If you're happy wielding a soldering iron, that might be the way forward.

My old uni's oil baths were just a vat of water or oil above a homemade magnetic stirrer, with a circular immersion element running the rim of the base and a thermocouple-linked circuit to set the temperature. A tenth^[1] the price and better than low-end lab kit.

^[1]Prices may vary from memory and approximation

[nojay.livejournal.com]

Actually Cairmen's sous-vide bath used a PID controller that costs about 80-100 quid and that didn't include a stirrer unit so it ran into overshoot problems (it took longer to cool down than to heat up).

For 200 quid you get a waterbath that is designed for the job and should last decades even in the hands of the sixth year pupils. Anything you hack together from cheap commodity bits is going to be more fragile and require a lot of intervention to keep it to working and even then it is likely to be less reliable, especially if you're planning on running it for days on end.

I'm surprised there isn't a Ebay-style network of school and college lab technicians swapping and selling surplus stuff to each other; Usenet would work for this quite well, something along the lines of uk.advert.computers or similar.

[akicif.livejournal.com]

I think there was a JANet mailing list for such stuff once upon a time: there may be a JISC one these days....

[ffutures.livejournal.com]

There are dozens of the buggers for sale on ebay USA, but very few in the UK, and usually more expensive than buying from the usual suspects. I did once get a brand new 8L water bath on eBay for 45 quid plus postage - there was a guy who'd bought up some old stock from Griffin and George, an old model they were discontinuing. Unfortunately we only needed one at the time and I couldn't persuade my boss to buy a couple more in anticipation of needing more for our new labs.

There is a bulletin board for school technicians, but the only sur[plus stuff on offer in the last few months has been a set of imperial weights, which aren't really terribly useful.

The big problem about making my own is electrical safety testing - anything I made would have to be up to approved standards, and while it isn't terribly difficult to get hold of water heater elements, I greatly doubt I can build the thermostat unit to meet standards.

[ffutures.livejournal.com]

Forgot to add that there's a guy on eBay selling new Chinese 2.5L water baths for £100, but they're too small for my needs (we'd really like another 8 litre one, and another 4 or 8L one) and I get a bad vibe somehow, not sure why, and would be a bit dubious about doing business even if they were bigger.