Need advice on making test tubes

[minionhunter]

Hi,

I'm a chemist and I need to make some custom test tubes. I need 200-300 of them and I can't afford the $3/tube that the glassblower at work will charge me. They also don't need to be perfect. Just 10mm OD, and 100 (up to 110mm) long. No one I can find sells them for a price I can afford and the big glass companies don't give me the time of day.

I have all the borosilicate tubing I need, I can cut the tubes, I can melt the glass in the Bunsen burner, however half of the tubes I've made crack, so I need to figure out a cheap cooling oven. Do you think a toaster oven set to bake at 500 would work? I just need the tubes to work out and not crack on cooling so they leak on me. I can clean out the ones I make.

The glass is not real thick, and I don't need perfection, just for them to be water tight. I'm prototyping an assay I'm running on plants to eliminate animal drug testing from my work. Since this is way outside the box of an idea (but it is working so far) the funding is non-existent and I have to do everything myself.

Thanks for any help or advice you can offer me.

Sincerely,

Matt

[TlkQ]

Toaster won't work, Annealing point is 1050. You can flame anneal with a bushy, reducing flame. Coat it in soot basically and then burn it all off.

[BrassMonkey]

im not familiar with your field but u said your company/university had an in house glass setup. they will not let u use that or at least the kiln?

[menty666]

Cutting corners is bad, if you're going to heat them at all you'll want them annealed properly Though, you could likely batch anneal if someone'll give you a kiln rental slot.

$3.00 each actually isn't terrible given the cost of monotony and the fact you need them a consistent length. Remember, you're not just paying for a product, there's overhead of a business involved in pricing too.

Assuming you're not blowing these out, you have to round out the end, cut it, clean it up and polish then get it into the kiln. 4" is kind of short to hang on to, so it's a hassle for the blower to figure out how to deal with 200-300 of the things.

With the machines you get a lower cost because there aren't fingers to get burnt involved in the process

[minionhunter]

OK, so they do need to anneal is what I am getting. I was listening to a program that said you could place them in an oven at anything over 450, and missed the second part where you need to then heat that hotter later (anneal). OK.

I've made about 300 using pasteur pipettes melting the ends over, but overall made about 600-700 of them and most failed. The ones that worked, worked great. They still work, and I could just use those but they are too small it turns out. However the ones that cracked, most I could catch by eye, then I lost more when I put liquid in them. That would be fine, but the pasteur pipettes are not big enough for what I need (roots don't have enough space), the 13x100 tubes you can buy are OK, but I'm trying to minimize the amount of compound I am using so I need to go down to 10x100 and no one sells them that I can find (just 10x75 which are too short). So it seems like making my own needs to be the way. Fancy and volume saving would be tapered point on the end, but I don't need that, I don't need pretty or smooth or anything other than functional.

I never said that $3 was a bad price, he likely would do it for $2/tube because his pattern is to over quote then charge less. The glass blower on campus is a nice guy, and I use him a lot for my glassware needs (keep the glass guys employed and they charge less than the big houses for most stuff) but I know if I asked about using his kiln, the answer would be no. The glass blower where I got my PhD, would have shown me how to do it and let me use his shop and maybe charged me $20 if anything at all (since I had my own tubing). Just different people. Even if my current guy would let me use his kiln, there is no way I could get them to him without them cracking based on the pasteur pipettes and the tubing I have is even thicker. And he would not let me use his shop to do it, no way.

So from above coat the tube end in soot with the flame, then burn it off (same part of the flame or a different part or different flame? Then what, just let them cool in the open air?

Also FWIW - I'm a Med Chemist, PharmD, PhD, postdoc at UMN. I realize I am NOT the expert here, so I'm asking questions and I sincerely appreciate the advice.

[Bo Diddles]

Putting them between ceramic fibre blankets or in vermiculite to cool may work, but you'd still need to properly anneal them later.

[Role]

The amount of labor to make those tubes is just not worth it.

12 mm X 100 mm are available for 23 cents each....

You're going to tell me that you cannot put an equal amount
of compound into a 12 x 100 as you would into a 10 x 100 ?????

[minionhunter]

Putting them between ceramic fibre blankets or in vermiculite to cool may work, but you'd still need to properly anneal them later.

OK, I'll try the vermiculite, I've got two cubic feet of that lying around the lab. I'll see how much my guy will charge to anneal them, but he won't like it.

[LarryC]

$2 a piece is a very reasonable price for the job. Why not just pay him to do it? Later on you may need something more complex and this would be a good working relationship to foster.

[minionhunter]

The amount of labor to make those tubes is just not worth it.

12 mm X 100 mm are available for 23 cents each....

You're going to tell me that you cannot put an equal amount
of compound into a 12 x 100 as you would into a 10 x 100 ?????

Its not a question of can I do it or not, but conserving the amount of drug used. Volume increases with the square of the radius, so its going to be about 1mL or more per tube at 12mm OD vs. 10mm OD. Times 100 is at least 100mL, and that is 100mL more solution I need to make and consume drug to fill. At nanomolar concentrations that won't matter too much, but at micromolar and higher concentrations which is what the plants seem to need to respond to here, it adds up quick. Would you want to use an extra half gram of your favorite drug when you don't have to?

Then when you consider that when you make brand new compounds (the desired endpoint is an assay where you can test unknown new compounds), you have even less, sometimes only a few milligrams, and you can't just go out and buy them, you have to make them. I would say, whatever work you put into your most complex glass pieces, multiply the blood, sweat, tears and treasure by 10 (at least) to get an idea of what it involves to make a new compound (potential drug) that only you have the worlds only supply of. How careful do you want to be with that tiny little supply? Then you can get an idea that the time to make these glass tubes, to me, while significant, is relatively NOTHING.

My current assay is just proof of concept and uses a LOT of compound. I'll have to switch it to a plant that I can use very tiny tubes to test in (like capillary tubes about 1-2mm in diameter). However I'm going simple as can be at this point.

Does this help with why I need what I need? I've done quite a lot of work and thinking about this, if I need 10x100 that is what I need. Yes 12x100 would work, and maybe I will use that (do you have a link, I've found 10x100 links that turned out to be not what was stated, usually plastic), but I need to conserve volume if possible.

[minionhunter]

I'm not trying to come off as snippy, just I need something specific. Why is someone like me asking for help here? I think that people who do something all day everyday, or because it is the only thing they can do (because everything else bores them to tears), or because their passion for it is all consuming, are the best people to ask about a thing. I don't care how many degrees or certifications someone has, that does not tell me about them nor make me want to take their advice, their responses tell me about them and if I will trust them enough to try what they suggest (trust but verify).

Sooty flame
Vermiculite
see if my guy can anneal for me, I can work with that plan

Thanks to everyone for your kind and generous help.

Sincerely,

Matt

[TheGlassTree]

You could just buy a cheap used aim or skutt kiln for 200$ off craigslist...

[themoch]

what's your budget on these and what do you want the inner diameter to be?

i think i know a guy who can help you out at much less than $2/piece

[Shmart]

I'm surprised that they're cracking on you at all. you should be able to round them off and use them without annealing them. (i know that its not good practice)

Are they flat on the inside when you have finished? this may cause an acute edge which could lead to the end popping off.

Are you getting them too hot too quick? ( this is unlikely if you're actually using a bunsen burner.) could you explain what your using for heat or post a link to what your using?

I think you'd be struggling to make them with a bunsen burner, well done if you are. Are you definitely using boro?
I used to make burettes out of soda and boro so i'm pretty sure that the pipettes could be the same.

I'm just guessing here, if you can give some more info on your process and how they're failing we may be able to help.

[Role]

Yes 12x100 would work, and maybe I will use that

Low alkali borosilicate, 23 cents each 21 cents each in volume.

12 x 100 Test tubes, boro

Google is your friend.

ETA:
I'm starting to think this is a joke like the guy that hooked his torch up backwards...
A PHD chemist that doesn't know where to get labware ?

[standard28]

If you are only using a bunsen and pulling them down then more then likely they are soft glass and they will crack more. I would not use s bushy or sooty flame. Just go in them in the middle and pull apart and place into vermiculite about half way. Some will break but most shouldn't. If you use borosilicate and you can get enough heat from the bunsen do the same and almost all of them should stay together. If you are moving your flame around you are just creating stress in other areas. Cut the tube so you get 2 per part and just pull down in the middle, gather the glass a bit and blow to get a radius then place in vermiculite.

I am a university glass blower. If I had a student that was trying this I would be more upset the he/she was doing this alone. I understand money is limited but you should talk with the glassblower. Tell him everything you are doing, he may even set you up in his shop and let you anneal them too....

Goodluck

[menty666]

Just out of curiosity, how were you cooling them? Laying them on the bench or keeping the hot end elevated to air cool?

[hashmasta-kut]

ya they shouldnt crack if air cooled right. way bigger stuff can be bench cooled, such as tube pulls, that rarely crack. try cooling them vertically, that leaves less stress in them.

[Billyben]

Would you want to use an extra half gram of your favorite drug when you don't have to?

Yes.

That aside, your pipettes are most likely soda lime glass and somewhat more prone to cracking. What are their dimensions? If you are dead set on making this work the above advice to simple split the tube in half to get two out of one is good. However all the pipettes I have seen are of course tapered on one end so maybe you would still only get one useable piece.

I have melted hundreds of pipettes on Bunsen burners (for fun) and never had one crack. I don't get why yours do. Soda glass, acute angles on the inside and extremely poor cooling?

Melt tip off, slight blow to round out acute angles, into vermiculite to cool. Batch anneal.

You could get a cheap kiln as stated, but really you could spend the same money just buying the tubes or getting them made for you.

Ring all the reps for the companies that sell your department science gear ThermoFisher, Global Science ect, tell them what you want and ask for a deal. Rep's will jump through hoops to sell you anything

[Islandglass Man]

So minionhunter phd You're complaining about $3 test tubes from an in house scientific glassblower. You have no idea how lucky you are to have an in house glass shop you should stick to chemistry. The glassblower on site has to charge an hourly rate and it will take time out of his day to make test tube. You don't work at wall mart science coast money I have dealt with chemists with your attitude and it's very disturbing when some phd thinks they are paying to much for apparatus. You might know wet chemistry but you don't have a clue about scientific glassblowing or it seems glass chemistry end of rant mr.phd

Bear

retired scientific glassblower