Does gas pressure effect the way the glass reacts to heat?

[jseid94]

Hey guys,
So I have been on the torch 6 months and mostly make pipes. The torch I use is a Bethlehem Stacks. I've noticed a few things when it comes to the flame and the way the glass reacts to the flame that I would appreciate some insight on.

First, when I use a larger flame, specifically with the bottom torch, I notice that I don't get sharp blue candles unless my oxy is turned way up. At that point, the glass gets so hot it just flops, no matter how thick. But when the oxy is at a normal level, the candles are yellow which I read means there is gas that isn't fully combusting.

Additionally, when I try to do Maria's and things like that, I notice that the glass gets hot and maluable but it doesn't get that natural flow like molten glass should and it makes it very difficult to do clean Maria's bc the glass gets creeses instead of flowing smoothly.

I have not been particular about my propane pressure and after reading a bit on this I suspect my propane is just too high and I need to lower the pressure to get the flame chemistry right and this will fix the issues I have with the glass and how it reacts.

I was just wondering if anyone had any insight they can add to my dilemma and what I've been experiencing.

Thanks so much guys,
Josh

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[snoopdog6502]

I'm not a big Bethlehem fan but I would use the recommended pressures set forth by the manufacturer.

Rather then write out a bunch of stuff that starts an argument here is a video. Learn what a neutral flame is to start.


https://www.youtube.com/watch?v=rHarXa12Gu0

[istandalone24/7]

what are you using for an oxygen source? oxycons, tanked etc.

if you need a quick way to dial in a certain flame, reducing, neutral, oxidizing etc use this:
https://glassalchemy.com/blogs/the-formula/glass-blowing-tutorial-setting-a-neutral-flame


i almost bought one of those stacks, the price is right but in the end went with another mirage.

[harpentuan]

In a related side note; that really is a nice torch you have jseid94 :fire

[lost nebula]

A neutral flame does not look the same on a Bethlehem compared to some other torches, beths do not need sharp blue candles to be neutral and they will run fine with some yellow in them as long as your not building up lots of carbon on the face your good.

To test for a neutral flame, Glass Alchemy recommends heating a rod of 987 Amazon Night to a warm orange glow, then allowing it to cool. If your flame is neutral, the rod should be the same color coming out of the flame as it was going into the flame. If the rod is a light sky blue or has a metalic sheen, the flame is reducing and needs to be adjusted. The most common fix is to decrease the propane content.
If the surface of the glass looks like an oil slick, decrease the propane at the torch.
If the surface of the glass is a heavy metalic, decrease the regulator in 1/4 pound increments.
If the surface of the glass is sky blue, it is very reducing. Decrease the propane at the regulator, usually in half: i.e. decrease from 2 pounds to 1 pound of pressure.
In some cases, increasing the oxygen will burn the extra propane in the flame resulting in a neutral flame.

Now that you know you have a neutral flame, I run 5gas/25oxy or 4gas/20oxy on my bravo most of the time but this is a low pressure torch so experiment. Bethlehem says you can go as low as 2gas/8oxy.

If you having trouble with things getting too floppy I'm pretty sure your too close to the candles. Bethlehem torches are not known for being stupid hot so back out a couple inches and see if you have better luck.

[aommaster]

Flame chemistry should not affect how your glass flows when shaping the maria. In order to get a smooth maria, you need to establish a good heat base in the glass first, before you compress your gather. [Edit: See Mute's reply below... my point is not entirely accurate]

Bethlehem torches are low velocity torches, which means that the gas escaping the torch is moving at a low speed. This has a few effects:
1. The heat can penetrate glass because there's more time for the heat to transfer between the gas and the glass
2. Candles do not necessarily represent the flame chemistry and you'll need to go back to basics as to what flame types are.

That is:
An oxidizing flame is rich in oxygen. Combustion of the gas is complete and there is surplus oxygen and results in a blue flame.
A reducing flame is poor in oxygen. Not all the fuel combusts completely, resulting in carbon monoxide and carbon (soot) formation.
A neutral flame has just enough oxygen to complete the combustion... eventually. So, you should have yellow candles, but further away from the flame, after all the gasses have had time to mix, it should be blue.

Or, use the advice from lost nebula, above to determine the flame type.

Additionally, for flame settings, use the settings from the Bethlehem, but back off a little bit on the pressures (0.5-1 psi for fuel, 1-3 psi for oxy, depending on your torch).

[Mute]

i agree its all about the heat base.

but in my opinion the flame chemistry absolutely effects the heat base along with the workers experience.

not only are there different flames settings such as reducing, neutral and oxidizing but each flame has a region of those 3 characteristics within them. there are illustrations that depict this.

different torches have differences in the regions of these characteristics, in relationship to the length of the region.

running the pressures at different levels (high and low) effects these regions.

it all effects the heatbase

and heatbase effects shaping.

[aommaster]

Fair point! I've added a small edit to my post above so people can read your reply too. Thanks Mute!

[BORO]

So I have use of a stacks when I'm in my home town. ( At 42degrees in glens falls)

When it was brand new, it never made any heat expansion noise. I shot this video the other day to try to catch the clicking sound. It sounds like a hot car exhaust. The video does not convay how loud it actually is. The stacks is SO loud on it's own it drounds out the "click". Running 25#s o2 and 4#s propane.

It would not be as big a issue, but it sounds just like cracking glass. Some days it's much much louder as well.

The stacks does not like low back pressure. When our dewer was at the end (50-80#s?) the regulator was at 25#s , but it would not melt in. Even tho the flame looked the same it was very very slow to heat. My Maria's were more wonky for sure. I thought it was me, but it was the end of the o2. (Sorry no janky pics) The bottom of the stacks really reminds me of a red max bottom flame.

If you watch this video, the center of the flame is blue, then turns pale as it heats up. I did not adjust it. I don't think that's the camera on the cell phone adjusting, it just changes atmosphere as it heats up.


https://m.youtube.com/watch?v=VqawDb5l9bY


I believe this video is a netrual flame , if not ever so slightly reducing. I adjust it to a more oxidizing flame right at the end. That final flame is plenty of 02 for 99% of what you need to do on the bottom. If I want to make Maria's , I use the top fire. It gets plenty big enough. The top fire has a much sharper flame shoulder, so you get a hot ring with a cold edge. That equals a crispy Maria. Make sure you have a hot ring before you push it together or it may be wonky. Sometimes a slight puff as you start to push can also help keep the Maria hollow if that is the look your shooting for.


As far as the issues with this one, we are waiting to hear back from the company. It almost feels like the torch cracked between drilled holes? I can see hairlines, but I need a eye loop and a good face cleaning to be sure if it has damage. It was never run with soft or short candles. Hard to say what's up ,but it is not operating like it was when it was new.


92761

If I wanted even finer Maria's, I would switch to a pre mix hand torch.

[jseid94]

Thanks so much for all the insight! I changed up my pressure to reflect the recommendation from Bethlehem. I will let you know how it goes once I'm back on the torch tomorrow!

Beat,
Josh

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