magnetic stirrer questions

q_x · Dec 18, 2008

I have one!

True: the dip-in things not always work for me. I've tried even liquid latex emulsion. Failure.

I use currently plastic drink straw. It is thin, cheap and easy. You can obtain one in any pub/coffee/McDonalds. Sealed with Zippo or other flame, later squeezed with pilers. I've formed the ends in flat shape to have intensive stirring. Also some enclosed air seems to be reducing friction with glass.
I used part of ordinary nail as stirring bolt.
Do you have any "normal" idea how to make stirring plate hot?
Cheers,
Luke

michaelbsc · Dec 18, 2008

jeroldharter said:
With some luck, you can get a high quality magnetic stirrer on Ebay for $20. I have 2 of them and they work great. I bought several stir bars from an online scientific supply store as well as a magnetic plastic wand to retrieve the stir bar.

Yea, but you gotta be lucky, or at least not bidding against me for one. I've been looking off and on for months, being the ubercheapskate that I am, and every time I put in a bid the price goes through the roof. The week before I bid on one some guy gets one for fifteen bucks, but you would think the one I bid on is the last one on the planet. I'll get outbid by $50.

Of course, I've also gotten a few great steals on eBay. So in the long run it's about even. But I still don't have a stir plate.

MB

Larry Bullis · Dec 18, 2008

Have you tried Labx? I haven't looked there for a long time, but I've got some great deals on lab equipment. www.labx.com

eli griggs · Dec 18, 2008

No, I haven't tried Labx but thanks for the link, I've made a book-mark for future reference.

I've not done anything since my last post, having been laid-up all day with a migraine but I'll try a new glass tube with magnet and a heat-shrink with hot glue shavings mild steel. I might try a small magnet between two short pieces of steel rod in the heat shrink. I'm thinking the slight middle budge from the magnet will make a decent pivot point; we'll see.

About bamboo tongs, why not try a piece of bamboo tooth pick instead of paper clip to keep the plastic tip on? It's very strong and probably won't swell enough to split the arm.

Eli

Larry Bullis · Dec 18, 2008

eli griggs said:
About bamboo tongs, why not try a piece of bamboo tooth pick instead of paper clip to keep the plastic tip on? It's very strong and probably won't swell enough to split the arm.
Eli

Good idea. The drill press could use some exercise. A bit of glue on the toothpick could bond the toothpick to the bamboo stick, and hold the whole thing together. If this works, it will eliminate one of the most horrible of all the crosses I must bear.

Thanks.

Larry

Kirk Keyes · Dec 19, 2008

How about just buy one - http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=330272421718

They last forever, as long as you don't misplace them...

eli griggs · Dec 19, 2008

Kirk, I pulled the trigger on one of these after your post, thanks for the link.

I still have to come up with something until it arrives though.

Cheers, Eli

michaelbsc · Dec 19, 2008

eli griggs said:
About bamboo tongs, why not try a piece of bamboo tooth pick instead of paper clip to keep the plastic tip on? It's very strong and probably won't swell enough to split the arm.

I have to agree with Larry on this. Thanks for the tip. This is one of the best simple ideas to solve a maddening problem I've seen in a long time. I owe you one for this.

Michael

Larry Bullis · Dec 19, 2008

The choice of glue would be important. I clean these tongs by tossing them in the holding tray which takes the outflow when the last batch of RC is washing. The glue has to be very waterproof. Boat glue. I have a tub of weldwood powder and plenty of time for them to set over christmas. I've always been partial to that glue (beware the formaldehyde while it's wet, though) since my uncle and I built a boat with it when I was 11. That was in 1953-54. It is amazing that product is still around. Somebody must still be using enough of it to keep it in production.

CBG · Dec 19, 2008

Funny, how very informative one thread can be. So many good ideas here.

Thanks,

C

Smudger · Dec 19, 2008

New tips for tongs..

I have re-tipped most of my stainless steel and bamboo tongs with plain old hotglue. A piece of release paper between the jaws as it sets makes a perfectly uniform gripping surface that's kind to my prints.

Larry Bullis · Dec 19, 2008

Smudger said:
I have re-tipped most of my stainless steel and bamboo tongs with plain old hotglue. A piece of release paper between the jaws as it sets makes a perfectly uniform gripping surface that's kind to my prints.

Now that's interesting! Might be better than handle dip/liquid tape.

RJS · Dec 20, 2008

Since my Nikor magnetic stirrer gave up I've been using theold Kodak paddle. But this makes me wonder about the hand held stirring/mixing machines sold for cooking. Is there any reason one couldn't do double duty? I would guess that prompt washing in hot water would remove any toxic chemicals. I see lots of cordless mixers on the market and have been wanting anexcuse to get one for the kitchen.

Anyone tried this?

Larry Bullis · Dec 20, 2008

RJS said:
Since my Nikor magnetic stirrer gave up I've been using theold Kodak paddle. But this makes me wonder about the hand held stirring/mixing machines sold for cooking. Is there any reason one couldn't do double duty? I would guess that prompt washing in hot water would remove any toxic chemicals. I see lots of cordless mixers on the market and have been wanting anexcuse to get one for the kitchen.

Anyone tried this?

You just need to be sure that the "beater" doesn't beat a lot of air into it.

eli griggs · Dec 20, 2008

You just need to be sure that the "beater" doesn't beat a lot of air into it./QUOTE]

How would this be different than the vortex created by the stir?

Eli

Larry Bullis · Dec 20, 2008

eli griggs said:
You just need to be sure that the "beater" doesn't beat a lot of air into it./QUOTE]

How would this be different than the vortex created by the stir?

Eli

Click to expand...

I think it would be a lot different because as the blades cut through the liquid, there probably would tend to be a void at the trailing edge, which I would think would draw air in and mix it up pretty well. You are mixing at the top of the container. If you are able to get the blades completely submerged, it might work better. The stir bar is at the bottom so that isn't as much an issue.

Anyway, I don't get much of a vortex. I mix in a 2000ml Volrath SS beaker (or 2 of them for 4 liters), and I leave a thermometer leaning from the bottom on one side across the lip of the other side. Then I adjust the rate of spin to where there doesn't appear to be any disturbance sufficient to get the air in. I'm sure that some air does get in, but I don't think much does.

eli griggs · Dec 20, 2008

Thanks for the response. My mixer, with a liter of water creates a strong vortex to the bottom of the Pyrex measuring cup. Perhaps I should use a deeper, less wide beaker for mixing to avoid or lessen the vortex effect.

Eli

Larry Bullis · Dec 20, 2008

eli griggs said:
Thanks for the response. My mixer, with a liter of water creates a strong vortex to the bottom of the Pyrex measuring cup. Perhaps I should use a deeper, less wide beaker for mixing to avoid or lessen the vortex effect.

Eli

Or just put something in there to confuse the flow a bit. When you get your variable speed working, it will be a lot better for mixing photo chemicals. Eggwhites? that's another matter!

eli griggs · Dec 21, 2008

A small update; I've found the correct socket at last for variable control so that's taken care of and a good thing, as this is the timing unit I want to use for controlling a point-source enlarger, (but that's another thread).

By-the-way, there are about 28 power sockets on this thing, in about four groups of 6-7 each. How the designer/photographer that built it might have used all that capacity is a mystery to me.

The spinners I have now do best around 55-60 volts with a slow start rpm but I'm wondering if part of the problem is that my magnets are either too strong, too close together on top of the fan, kissing in fact, or if I should change the side-by-side arrangement of poles from, ie N-N to N-S?

I've also switched beakers from the Pyrex 1lt measuring cup for a heavy glass, cone shaped, Kodak 32oz/1lt unit that has a better spout, but, of course, no handle.

Any ideas?

Eli

magnetic stirrer questions

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