Melting Lead With Only Limited Facilities
Proud Mary, Fri Jan 11 2019, 10:18PMDoes anyone have any recent practical experience with melting lead with only limited facilities that they could share with me, please?
The problem: To cast a lead block containing six channels in which GM tubes are to be inserted to form a Bruno Rossi type cosmic ray muon cascade detector.
Facilities: Either (a) my kitchen gas stove OR (b) a large Camping Gaz type butane cylinder with a burner mounted on top.
Note: I live in a retirement complex and have a very small workshop in my flat/apartment. I do not have my own garden/yard.
The metal to be melted down is assorted lead scrap, with typical surface oxidation but otherwise very clean.
I am thinking to use a stainless steel saucepan with metal lug handles (i.e. no plastic or wood fittings).
I am aware of the toxicity of lead fumes, though it can hardly be worse than half a century of soldering!
I am thinking of making a mould for my detector block from fire clay and steel tubes (for the GM tube channels) but am concerned that the fire clay might explode due to trapped air or moisture. Would the cooling lead contract around the steel tubes?
Any thoughts based on practical experience will be very welcome - Stella.
Re: Melting Lead With Only Limited Facilities
Blackcurrant, Sat Jan 12 2019, 02:02AM
Couple of things that come to mind are
You could bake the mould first in an oven for a bit, get rid of any damp.
Make sure the mould is strong it's going to have weight pushing on the sides.
The hollow tubes may try to float up!
Cooker should be able to melt it, but I may be remembering a lead/tin mix.
If there is any rubbish in the lead it will smoke.
When you have melted the lead it may have scum on top so just skim this stuff off before pouring.
The lead will shrink while cooling so slightly overfill.
Use a pan with a pouring lip if you can.
Have your mould siting on a metal tray so if there is any spillage it's not going to get far.
If it's a lot of lead it's going to get real heavy and take ages to cool.
Try a small amount of lead first pour into a simple mould, just to see how things go.
Polycarbonate Face Screen , Welders Gauntlet. Etc
there will be a ton of stuff on youtube
Blackcurrant, Sat Jan 12 2019, 02:02AM
Couple of things that come to mind are
You could bake the mould first in an oven for a bit, get rid of any damp.
Make sure the mould is strong it's going to have weight pushing on the sides.
The hollow tubes may try to float up!
Cooker should be able to melt it, but I may be remembering a lead/tin mix.
If there is any rubbish in the lead it will smoke.
When you have melted the lead it may have scum on top so just skim this stuff off before pouring.
The lead will shrink while cooling so slightly overfill.
Use a pan with a pouring lip if you can.
Have your mould siting on a metal tray so if there is any spillage it's not going to get far.
If it's a lot of lead it's going to get real heavy and take ages to cool.
Try a small amount of lead first pour into a simple mould, just to see how things go.
Polycarbonate Face Screen , Welders Gauntlet. Etc
there will be a ton of stuff on youtube
Re: Melting Lead With Only Limited Facilities
klugesmith, Sat Jan 12 2019, 06:50AM
Good to see you, Stella. Happy new year!
Could you skip the melting, and pack lead shot or lead wool around the tubes?
klugesmith, Sat Jan 12 2019, 06:50AM
Good to see you, Stella. Happy new year!
Could you skip the melting, and pack lead shot or lead wool around the tubes?
Re: Melting Lead With Only Limited Facilities
klugesmith, Sat Jan 12 2019, 04:13PM
If you use (untapered) steel tubes as cores, expect them to stay in the cast lead block forever. BC makes good point, to secure them against floatage when you pour. Could be filled with sand to seal the bottom end. Can the outer mould be a tin can or other metal box (even aluminium) that would be OK to stay with the lead block forever? Initially surrounded by loose sand or clay for safety.
You don't need to pour the whole block at once. Could do in in lifts as small as you want, melting the lead in an iron plumber's ladle, and pouring through a piece of window screen to filter out most of the dross.
klugesmith, Sat Jan 12 2019, 04:13PM
If you use (untapered) steel tubes as cores, expect them to stay in the cast lead block forever. BC makes good point, to secure them against floatage when you pour. Could be filled with sand to seal the bottom end. Can the outer mould be a tin can or other metal box (even aluminium) that would be OK to stay with the lead block forever? Initially surrounded by loose sand or clay for safety.
You don't need to pour the whole block at once. Could do in in lifts as small as you want, melting the lead in an iron plumber's ladle, and pouring through a piece of window screen to filter out most of the dross.
Re: Melting Lead With Only Limited Facilities
2Spoons, Sun Jan 13 2019, 06:42AM
The fumes from molten lead are worse than from solder because 1) the temperature is higher and 2) Solder is only 40% Pb.
Do this either outside, or if you must use your kitchen do it under the extractor (at max).
Your mould should be hot when you pour your lead in - get it as hot as you can in your oven. Less likely to crack from thermal shock or have a steam explosion blow lead everywhere.
2Spoons, Sun Jan 13 2019, 06:42AM
The fumes from molten lead are worse than from solder because 1) the temperature is higher and 2) Solder is only 40% Pb.
Do this either outside, or if you must use your kitchen do it under the extractor (at max).
Your mould should be hot when you pour your lead in - get it as hot as you can in your oven. Less likely to crack from thermal shock or have a steam explosion blow lead everywhere.
Re: Melting Lead With Only Limited Facilities
Conundrum, Sun Jan 13 2019, 03:05PM
Can you not add some Bi to lower the melting point?
I have some here and you can source (haha) this from ye old fishing shoppe.
Though this is typically 97Bi3Sn this does not make a lot of difference and the resulting alloy is eutectic and shrink free if you get the initial proportions right.
Use some Fluxite(tm) flux to get a good result as this worked for me.
Also relevant: have some Pb "foil" from a failed roofing project if you can use it.
Guaranteed quality and very little oxidation that I can see, not sure on postage but can't see it being a major annoyance.
Re. casting etc. just be aware that fire cement *may* be OK provided it has completely cured but saucepans generally will not take the heat AT ALL especially if coated. Old iron one piece might be OK but beware of highly toxic fumes if there is any sort of non-stick coating.
This usually becomes a problem anywhere above 240C which is (I hope) well above even a hardened chef's typical food cooking temperature.
Canary, coal mine etc.
Conundrum, Sun Jan 13 2019, 03:05PM
Can you not add some Bi to lower the melting point?
I have some here and you can source (haha) this from ye old fishing shoppe.
Though this is typically 97Bi3Sn this does not make a lot of difference and the resulting alloy is eutectic and shrink free if you get the initial proportions right.
Use some Fluxite(tm) flux to get a good result as this worked for me.
Also relevant: have some Pb "foil" from a failed roofing project if you can use it.
Guaranteed quality and very little oxidation that I can see, not sure on postage but can't see it being a major annoyance.
Re. casting etc. just be aware that fire cement *may* be OK provided it has completely cured but saucepans generally will not take the heat AT ALL especially if coated. Old iron one piece might be OK but beware of highly toxic fumes if there is any sort of non-stick coating.
This usually becomes a problem anywhere above 240C which is (I hope) well above even a hardened chef's typical food cooking temperature.
Canary, coal mine etc.
Re: Melting Lead With Only Limited Facilities
klugesmith, Sun Jan 13 2019, 06:07PM
With regard to evaporation, lead is an exceptionally nonvolatile metallic element.
Its vapor pressure _at melting point_ ranks near the bottom -- look it up. 2nd chart here: Not in a class with gallium and indium, but many orders of magnitude lower than toxic metals known for fume hazards (cadmium and zinc).
It's more important not to be cavalier about personal protective equipment, to avoid burning yourself in an accident.
Beware of free advice on the Internet.
I like Andre's suggestion of using bismuth. Why not pure bismuth, or some prepared low-melting alloy? See what the user's manual for Cerrobend (aka Wood's metal, MP 158 degrees F), which has lots of cadmium, say about shop ventilation.
I guess lead is traditionally first choice for radiation shielding, but expect bismuth isn't far behind in those properties. Heaviest known stable isotope, if you don't count the recently discovered decay with half life greater than 1e18 years.
klugesmith, Sun Jan 13 2019, 06:07PM
With regard to evaporation, lead is an exceptionally nonvolatile metallic element.
Its vapor pressure _at melting point_ ranks near the bottom -- look it up. 2nd chart here:
Not in a class with gallium and indium, but many orders of magnitude lower than toxic metals known for fume hazards (cadmium and zinc). It's more important not to be cavalier about personal protective equipment, to avoid burning yourself in an accident.
Beware of free advice on the Internet.
I like Andre's suggestion of using bismuth. Why not pure bismuth, or some prepared low-melting alloy? See what the user's manual for Cerrobend (aka Wood's metal, MP 158 degrees F), which has lots of cadmium, say about shop ventilation.
I guess lead is traditionally first choice for radiation shielding, but expect bismuth isn't far behind in those properties. Heaviest known stable isotope, if you don't count the recently discovered decay with half life greater than 1e18 years.
Re: Melting Lead With Only Limited Facilities
Conundrum, Mon Jan 14 2019, 05:48AM
I think that might be the problem. Bi is slightly radioactive.
Conundrum, Mon Jan 14 2019, 05:48AM
I think that might be the problem. Bi is slightly radioactive.
Re: Melting Lead With Only Limited Facilities
klugesmith, Tue Jan 15 2019, 03:19AM
Could not resist playing with the "slightly radioactive" numbers that I just learned about.
Natural bismuth is 100% Bi-209, long thought to be the heaviest known stable isotope.
Not until about 2003 was its alpha decay discovered, with half life of 1.9e19 years (more than a billion times the age of the universe).
For use as a radiation shield, in medicine or in Stellas' flat, bismuth might as well be nonradioactive.
Here are some unreviewed conclusions to put that in perspective.
1. The total activity of 1 kilogram of bismuth is 1/300 Bq, also known as 91 femtocuries. That's one decay every 5 minutes, somewhere within the volume.
2. Range of 3.14 MeV alpha particles is about 1.83 cm in air, and 0.00088 cm in bismuth.
3. A one-kg cube of Bi would have edge length 4.68 cm, surface area 131.5 cm^2.
The skin volume from which alpha particles might escape into air (with some energy left) contains 1.13 grams of metal, amounting to 3.8 uBq (1e-16 Ci).
About every 3 days, on average, one alpha particle would escape from somewhere on the cube.
klugesmith, Tue Jan 15 2019, 03:19AM
Could not resist playing with the "slightly radioactive" numbers that I just learned about.
Natural bismuth is 100% Bi-209, long thought to be the heaviest known stable isotope.
Not until about 2003 was its alpha decay discovered, with half life of 1.9e19 years (more than a billion times the age of the universe).
For use as a radiation shield, in medicine or in Stellas' flat, bismuth might as well be nonradioactive.
Here are some unreviewed conclusions to put that in perspective.
1. The total activity of 1 kilogram of bismuth is 1/300 Bq, also known as 91 femtocuries. That's one decay every 5 minutes, somewhere within the volume.
2. Range of 3.14 MeV alpha particles is about 1.83 cm in air, and 0.00088 cm in bismuth.
3. A one-kg cube of Bi would have edge length 4.68 cm, surface area 131.5 cm^2.
The skin volume from which alpha particles might escape into air (with some energy left) contains 1.13 grams of metal, amounting to 3.8 uBq (1e-16 Ci).
About every 3 days, on average, one alpha particle would escape from somewhere on the cube.
Re: Melting Lead With Only Limited Facilities
Proud Mary, Sun Jan 20 2019, 02:01AM
Thanks for all your helpful suggestions, which I have thought over before replying. I'm not in a hurry, so I will build up my lead block in layers over a few weeks, so I need not have to deal with much molten metal at any one time.
There is a charity shop/thrift shop up the road, so I'll keep my eyes open for an old iron pan with a pouring lip to melt my lead, which is in good clean condition on a roll intended for roofing.
I am not worried about alpha disintegrations, as I am using big Russian GM tubes which have metal casing.
I am making two detector assemblies - Detector A with the GM tubes housed in a lead block, and Detector B (equal and opposite) detector having tubes in an identical geometric arrangement but assembled on a clear acrylic frame.
Digital signal processing will allow the tubes to be configured in many ways, and I shall be copying other peoples' circuits for this, as I am not up to designing this part of it myself.
My idea is to have a window sill observatory consisting of the cosmic ray and terrestrial radiation monitors, a VLF Sudden Ionospheric Disturbance (SID) detector fed by an aluminium hoolahoop loop antenna, a terrestrial magnetism fluxgate magnetometer (both vertical and horizontal components) detector using Speake sensors and electronics (which comes as a DIY kit from Speake & Co. 6 Firs Rd, Llanvapley, Abergavenny NP7 8SL.) and an infrasonic detector for detecting large meteor strikes into the atmosphere (and blast overpressure!!!!)
I hope, in time, to put my observatory online in real time, so my data can be compared with that of other observatories.
Proud Mary, Sun Jan 20 2019, 02:01AM
Thanks for all your helpful suggestions, which I have thought over before replying. I'm not in a hurry, so I will build up my lead block in layers over a few weeks, so I need not have to deal with much molten metal at any one time.
There is a charity shop/thrift shop up the road, so I'll keep my eyes open for an old iron pan with a pouring lip to melt my lead, which is in good clean condition on a roll intended for roofing.
I am not worried about alpha disintegrations, as I am using big Russian GM tubes which have metal casing.
I am making two detector assemblies - Detector A with the GM tubes housed in a lead block, and Detector B (equal and opposite) detector having tubes in an identical geometric arrangement but assembled on a clear acrylic frame.
Digital signal processing will allow the tubes to be configured in many ways, and I shall be copying other peoples' circuits for this, as I am not up to designing this part of it myself.
My idea is to have a window sill observatory consisting of the cosmic ray and terrestrial radiation monitors, a VLF Sudden Ionospheric Disturbance (SID) detector fed by an aluminium hoolahoop loop antenna, a terrestrial magnetism fluxgate magnetometer (both vertical and horizontal components) detector using Speake sensors and electronics (which comes as a DIY kit from Speake & Co. 6 Firs Rd, Llanvapley, Abergavenny NP7 8SL.) and an infrasonic detector for detecting large meteor strikes into the atmosphere (and blast overpressure!!!!)
I hope, in time, to put my observatory online in real time, so my data can be compared with that of other observatories.
Re: Melting Lead With Only Limited Facilities
Conundrum, Sun Jan 20 2019, 05:36AM
Interesting, thanks for sharing!
Sounds similar to something I was planning to build but in my case using very small SBM-21 tubes originally intended for portable dosimeters.
Note: I did eventually managed to reconstruct the circuit for the modules in those red counters.
Its actually a unijunction transistor in there with some very basic C-W and other parts, also explains why the module needs 9V as transistor will fire with less but output becomes unpredictable.
Incidentally do you have datasheets for the other >700V submin GM tubes please?
My current test circuit is a variant of earlier idea using Supertex (tm) now Microchip HV850 using active rectification via optocoupler to reduce losses at the cost of output current.
Runs on +4V2 which is a substantial improvement but still need to work out the bugs.
Conundrum, Sun Jan 20 2019, 05:36AM
Interesting, thanks for sharing!
Sounds similar to something I was planning to build but in my case using very small SBM-21 tubes originally intended for portable dosimeters.
Note: I did eventually managed to reconstruct the circuit for the modules in those red counters.
Its actually a unijunction transistor in there with some very basic C-W and other parts, also explains why the module needs 9V as transistor will fire with less but output becomes unpredictable.
Incidentally do you have datasheets for the other >700V submin GM tubes please?
My current test circuit is a variant of earlier idea using Supertex (tm) now Microchip HV850 using active rectification via optocoupler to reduce losses at the cost of output current.
Runs on +4V2 which is a substantial improvement but still need to work out the bugs.
Re: Melting Lead With Only Limited Facilities
Carbon_Rod, Tue Jan 22 2019, 07:53AM
Check out the youtube tutorials on bullet casting.
They usually have great tips for using candle soot as a mold release agent, and burning sawdust to help clean off the slag.
One can also get a melting-furnace with Ti alloy crucibles used for solder, and they range in 1oz to over 30lb capacities (1500w units are under $200 delivered).
Happy 2019 =)
Carbon_Rod, Tue Jan 22 2019, 07:53AM
Check out the youtube tutorials on bullet casting.
They usually have great tips for using candle soot as a mold release agent, and burning sawdust to help clean off the slag.
One can also get a melting-furnace with Ti alloy crucibles used for solder, and they range in 1oz to over 30lb capacities (1500w units are under $200 delivered).
Happy 2019 =)
Re: Melting Lead With Only Limited Facilities
Proud Mary, Wed Jan 23 2019, 11:03PM
Do you have a type number for that part?
GM tubes only need microamps to power them. You could put a voltage doubler on the Mains, which in actual practice gives a peak voltage of just about 600V. I have done this with good effect, using an inexpensive miniature PCB-type 240:240 transformer with a fuse in the lead, and then picked off the desired voltage with a resistor and Zener, or series Zeners that you can tap down to have outputs for different types of tubes. If you go for fixed outputs, 350V, 450V and 600V will take you onto the plateau of most halogenated tubes. Antique organic quench tubes usually require much higher voltages, 1kV, or even 2kV, in a few cases I can think of.
Proud Mary, Wed Jan 23 2019, 11:03PM
Conundrum wrote ...
Interesting, thanks for sharing!
Incidentally do you have datasheets for the other >700V submin GM tubes please?
Interesting, thanks for sharing!
Incidentally do you have datasheets for the other >700V submin GM tubes please?
Do you have a type number for that part?
GM tubes only need microamps to power them. You could put a voltage doubler on the Mains, which in actual practice gives a peak voltage of just about 600V. I have done this with good effect, using an inexpensive miniature PCB-type 240:240 transformer with a fuse in the lead, and then picked off the desired voltage with a resistor and Zener, or series Zeners that you can tap down to have outputs for different types of tubes. If you go for fixed outputs, 350V, 450V and 600V will take you onto the plateau of most halogenated tubes. Antique organic quench tubes usually require much higher voltages, 1kV, or even 2kV, in a few cases I can think of.
Re: Melting Lead With Only Limited Facilities
Proud Mary, Wed Jan 23 2019, 11:05PM
Happy New Year to you too! I would never have thought of bullet vasting. without your suggestion. I'll have a look on YouTube as you suggest. Thank you.
Proud Mary, Wed Jan 23 2019, 11:05PM
Carbon_Rod wrote ...
Check out the youtube tutorials on bullet casting.
They usually have great tips for using candle soot as a mold release agent, and burning sawdust to help clean off the slag.
One can also get a melting-furnace with Ti alloy crucibles used for solder, and they range in 1oz to over 30lb capacities (1500w units are under $200 delivered).
Happy 2019 =)
Check out the youtube tutorials on bullet casting.
They usually have great tips for using candle soot as a mold release agent, and burning sawdust to help clean off the slag.
One can also get a melting-furnace with Ti alloy crucibles used for solder, and they range in 1oz to over 30lb capacities (1500w units are under $200 delivered).
Happy 2019 =)
Happy New Year to you too! I would never have thought of bullet vasting. without your suggestion. I'll have a look on YouTube as you suggest. Thank you.
Re: Melting Lead With Only Limited Facilities
Conundrum, Mon Jan 28 2019, 03:36AM
My uRADMonitor is up...
Conundrum, Mon Jan 28 2019, 03:36AM
My uRADMonitor is up...
Re: Melting Lead With Only Limited Facilities
Sulaiman, Mon Jan 28 2019, 06:19AM
Rather than the cost of an iron ladle and the risk of voids in the casting,
could you not just wrap with lead sheet ?
e.g.
Sulaiman, Mon Jan 28 2019, 06:19AM
Rather than the cost of an iron ladle and the risk of voids in the casting,
could you not just wrap with lead sheet ?
e.g.
Re: Melting Lead With Only Limited Facilities
Conundrum, Sat Feb 02 2019, 06:09AM
Has some lead sheet here.
Also yes BiInSn layered with Pb works if you want to build a shield without all the hassle of having to machine lead. Plus its easily reconfigurable if you screw up as long as you layer some sort of high temperature tape between the various layers.
I have a formula here someplace for a low indium (ie cheaper) alloy which still melts at sensible temperatures.
Conundrum, Sat Feb 02 2019, 06:09AM
Has some lead sheet here.
Also yes BiInSn layered with Pb works if you want to build a shield without all the hassle of having to machine lead. Plus its easily reconfigurable if you screw up as long as you layer some sort of high temperature tape between the various layers.
I have a formula here someplace for a low indium (ie cheaper) alloy which still melts at sensible temperatures.
Re: Melting Lead With Only Limited Facilities
Proud Mary, Sun Feb 03 2019, 09:59AM
Hi Sulaiman,
I haven't rushed into replying because I can't quite see what effect using rolled sheet lead (with all its air gaps and inhomogeneities) would have on a Bruno Rossi type EM cascade detector.
Anyone wondering what a Rossi-type cascade detector is, and how it works when formed from a solid block of lead, might want to look here:
physicsopenlab.org/2016/04/12/cosmic-rays- cascade/
Proud Mary, Sun Feb 03 2019, 09:59AM
Sulaiman wrote ...
Rather than the cost of an iron ladle and the risk of voids in the casting,
could you not just wrap with lead sheet ?
e.g.
Rather than the cost of an iron ladle and the risk of voids in the casting,
could you not just wrap with lead sheet ?
e.g.
Hi Sulaiman,
I haven't rushed into replying because I can't quite see what effect using rolled sheet lead (with all its air gaps and inhomogeneities) would have on a Bruno Rossi type EM cascade detector.
Anyone wondering what a Rossi-type cascade detector is, and how it works when formed from a solid block of lead, might want to look here:
physicsopenlab.org/2016/04/12/cosmic-rays- cascade/
Re: Melting Lead With Only Limited Facilities
Adam Munich, Fri Feb 22 2019, 06:40PM
I remember making a lead box back when I was building that x-ray machine years ago. A propane burner outdoors with a coffee can seemed to suffice. The hardest thing really was making a suitable mold to pour it into -- any sort of plaster mold must be incredibly dry or the lead will boil the water out and make swiss cheese from the part.
Adam Munich, Fri Feb 22 2019, 06:40PM
I remember making a lead box back when I was building that x-ray machine years ago. A propane burner outdoors with a coffee can seemed to suffice. The hardest thing really was making a suitable mold to pour it into -- any sort of plaster mold must be incredibly dry or the lead will boil the water out and make swiss cheese from the part.
Re: Melting Lead With Only Limited Facilities
Conundrum, Fri Feb 22 2019, 07:37PM
Same with any metal casting. Water is a *MAJOR* problem and extreme safety risk.
Conundrum, Fri Feb 22 2019, 07:37PM
Same with any metal casting. Water is a *MAJOR* problem and extreme safety risk.
Re: Melting Lead With Only Limited Facilities
2Spoons, Fri Feb 22 2019, 09:25PM
The link shows a successful experimental setup using multiple sheets of lead above scintillators, so it would seem reasonable that rolled lead sheet would work for you too.
2Spoons, Fri Feb 22 2019, 09:25PM
The link shows a successful experimental setup using multiple sheets of lead above scintillators, so it would seem reasonable that rolled lead sheet would work for you too.
Print this page