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LaserMakerMaybe 2022-03-27 7:21pm

Beginner question on torch and O2 selection.
Hi all,

Sorry for any noob questions in advance :).

First, I am looking for suggestions on what torch I should get for starting out on scientific lampwork for borosilicate.
Second, I am looking for suggestions on what oxygen system, tanked of concentrator, I should use.

Full Details:
My main purpose for the torch will be in building a vacuum tight laser tube. The project involves only borosilicate tubing, joining tubes together, making Tee joints, tungsten wire feedthroughs. Tubing sizes would mainly be 10mm OD x 2mm wall, a little with 8mm OD x 1mm ID capillary, and a maximum tube size of 50mm OD x 2mm wall.

I have not done any lampwork before this, I've only done a little experimentation to see if I could finish this project cheaply with only using simple hand propane torches, however it appears they just don't get hot enough to sufficiently finish Tee joints. Unless anyone knows of a good hot head (is that the right term?) that would work.

This is mostly a one off project, so I do not anticipate doing a whole lot of lampwork, but I do want to get an appropriate setup so that I can successfully complete the task.

Because I will not be using this system a lot, I do want to keep the cost seasonably low (if I can keep the full torch setup (torch, hose, regulators, O2) <$1k), So I am looking to get something a little above the minimum requirement.

For the first part of the question.
Right now I am looking at the Nortel mega minor, Bethlehem - Alpha, GTT bobcat or cricket. I'm open to opinions on which of these which of these will work best or if there are better options.
And as an additional consideration, I may try to do a little work with quartz, so it would be a bonus if they could work it also.

The second part of the question, should I use tanked oxygen or an oxygen concentrator. I think tanked oxygen could more easily provide more oxygen for more heat for working the few larger tubing, but oxygen concentrators might have less complexity from regulators and refilling. So the main question is what O2 system do you guys thing would be best for the appropriate torches for my infrequent use.

Sorry for the large essay here, I tried to give enough information, but I'm sure I forgot something. Let me know any other questions.
Any help and suggestions would help.

rcktscientist 2022-03-28 9:06am

I dig your enthusiasm. I'm the same way.

For boro, you need propane and oxy, no hot head or plumbers torch will work.
Your $1k budget will be challenging to meet since minimum prices for a torch and regulator will be around $200 and for the oxycon around $400. That only leaves $400 for workspace, materials, and tools/fixtures. Also, you haven't factored in the scrap you'll surely make while learning the basics.

The Bobcat is the hottest torch you listed. It can do small quartz and small/mid boro. I have a Bobcat and have been thinking about upgrading...

You sure outsourcing this work wouldn't be cheaper and wiser?

echeveria 2022-03-28 10:30am

Tanked oxy may be your best option to maximize your heat on a small torch. You will need an oxy regulator in that case.

Ditto on the outsourcing question, or maybe rent time in an existing studio.

Alaska 2022-03-29 1:36pm

Take a look at "The Melting Pot" glass site for your question.

LaserMakerMaybe 2022-03-29 4:54pm

Firstly, Thanks everyone for the responses!

rcktscientist. Sorry, I was a little unclear for budget, The <$1k would be just for the torch, oxygen, regulators and hoses. Just the torch setup. I had originally planned the whole project for $1k, which I am at now, so I'm just going to have to raise the budget to get the right torch setup. I think I already have all the other necessary stuff, I've got boro tubes, proper didymium glasses w/#3, swivel etc.
I might be able to have someone else do the work, but I kinda want to be able to say I did the project myself, and it feels like cheating to just outsource the most important part. I also might end up doing a bunch of experimenting with different designs, so don't want to have someone else build it several times. If I knew what I was doing it and just wanted the end produce, I would agree, that it probably would be much easier and cheaper to outsource it.

I'm near SW Michigan, I only know of one neon sign shop. Someone is setting up a new makerspace and I considered proposing they including some lampwork stuff, but I don't want to wait on that.

I actually did look at also posting my question on that site, but I can't make an account! It just shows a blank white screen and "File not found.". It does the same for all web browsers, mobile. Even the subforums, like "request Box" that might allow posting without an account wouldn't let me post.

rcktscientist 2022-03-30 8:57am

In that case, you may want to buy a hand torch/bunsen combo. Sealing tubing to tubing will be easiest with a hand torch and the bunsen will extend your working time. A National 3B-B torch with a few tips and a stand, an Eisco meker burner, and required hoses/fittings is a fantastic start for around $300. Plus, all easily resold. Regulators will run you about $200 for a set. So, your torch set up can be had for $500, not too bad.

Quick question:
How are you annealing finished work?... or in other words, how are you keeping internal stresses in the acceptable range? (to ensure fatigue from vacuum cycles does not lead to failure of a joint)

Btw, I had the same issue with The Melting Pot. No way to sign up, communicate, or anything.

phentron 2022-03-30 5:46pm

I assume you have studies methods of sealing tungsten with glass?
What type of optical window are you using? Quartz to glass seal is a bigger technical problem. Consider obtaining a pre-mounted quartz window (in a metal frame?) & glue, O-ring, etc this to the end of your tube.
How are you aligning the mirrors in the tube?

If you are considering high power laser, you will need water cooling coils in the tube – this will greatly increase glass working skills (& require kiln annealing).

If you are making a simple laser – no cooling coils, glass loops, etc, (my next comment is contriversal with many lampworkers) flame annealing is sufficient (Note: I did a 1 year scientific glass working course in the 1970’s, only used flame annealing & still have the items I kept – including condenser, flasks, etc) See flame annealing - Lampwork Etc. #27 & my thread Annealing, Glass Specs & Kilns - Lampwork Etc.,

Torch: I use a Herdie (a scientific glass blowing torch), I am not familiar with the above torches. Your torch should give a flame width equal to the tubing diameter you plane to use & go down to a very small flame, ideally to 3 – 4mm (1/8 inch), mine will do about 2mm diameter.

Oxycon/tank: I use an ocycon (10 lpm) but my torch is very oxygen hungry & had to add a reservoir/refill system. Oxycon deliver 96% O2 (at best) & many drop O2 % as you approach 10 lpm. 96% is sufficient for your seals, etc, but don’t go lower (100% is a hotter flame & I can tell the difference when I use tank).
For you, I suggest hiring tank & purchase reg. Have you considered hiring a studio? They will also have an annealer (but is it big enough for you laser?)

Final comment:
CO2 gas laser will not be a problem with your metal/glass seals, but if you are using smaller atoms like helium, neon (or experimental, like hydrogen/ gas mix? Gutsy) or using inert gas under pressure – your metal/glass seals need to be really good.


LaserMakerMaybe 2022-03-30 7:28pm

Thanks for those tips, I'll look into it.
For the short term I might just flame anneal. Eventually I might have to make a kiln, but if so it will be later in the project.

Yes, I have done a bit of online research for tungsten boro seals. Not a whole lot of info online, but enough that I think once I get a good torch I'll be able to figure it out. I'll probably use 0.2mm-0.4mm tungsten wire.
I will be having a brewster window on it. Right now I have several optical windows to try, I think all of them are Quarts/fused silica. I will be sealing the window to the tube with vacuum epoxy (Torr-seal/hysol 1C, suitable for this purpose).
The laser design will be very similar to a large Helium-Neon laser. Power is low enough that no active cooling is needed, so it keeps it much simpler.

I'm glad to hear you think flame annealing will be sufficient. Eventually I might want to make a kiln for full annealing, but I will worry about that later if I need to.
The gas is Helium at several torr. So leakage is an issue, especially long term. One solution for that is to minimize the number of electrical feedthroughs, right now looking at a minimum of 3-5. I've looked at neon sign electrodes, but I can't tell if they have any with borosilicate tubing, I think most are soft glass.
unfortunately I couldn't find any glassworking studios in my area.

At this point I am leaning towards tanked oxygen to ensure I can get enough heat when needed. I'll still have to see what tanked oxygen options and prices I have here.

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