Member postings for PatJ

Getting the right molding sand is really the most difficult part of casting things in my opinion.

Building a furnace and the associated equipment is a mechanical thing.

Making good green sand is somewhat of a magical black art.

Green sand (sand mixed with clay and a small amount of water) is dynamic, and since the water evaporates, you really need to mull green sand before you use it, generally adding a bit of water. A muller is like a large mixer, with one or more wheels, and plows to turn the sand over and then smear it with the wheel(s).

I was told by someone with a ton of iron experience in Australia that I should expect it to take up to 20 years to master green sand.

I first tried Petrobond (tm), which is an oil-based foundry molding sand.

Petrobond is a mix of clay, sand, non-detergent motor oil, and a slight amount of alcohol (I am told it should really be a special alcohol, and I will look up exactly what that type is).

One of the things the backyard casting community did not tell me was that if you pour iron (or perhaps bronze too) into Petrobond, and then open the mold while the casting is hot, a cloud of smoke will be created, and if you lean forward to look at the casting, the smoke can light off into a fireball. My eyebrows have since grown back, and luckily I saw the fireball coming and closed my eyes.

Every time I used Petrobond, the alcohol in it had dried out too much, and so it did not have any molding strength. Not knowing any better I added non-detergent 30 weight motor oil, and by adding too much oil, I ruined 5 gallons of Petrobond. I should have added alcohol only.

I am aware of one person in the UK who puts his Petrobond on a tarp on the floor, and then folds the tarp, and walks on the Petrobond, in order to mull it. He reports that this method works.

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There is something magical about pouring molten metal in a sand mold, and then breaking out the casting.

I know it is an ancient process.

As Noel says, temperature is all important when pouring aluminum (I use 356 alloy aluminum), and I pour at 1,350 F.

I heat the aluminum as fast as possible, with an oil burner that is often 12 minutes for a #10 crucible of AL, making sure not to overshoot, and then pour immediately.

If you wait around with hot aluminum, or overheat it, it absorbs gas like a sponge.

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Edited By PatJ on 02/07/2022 12:47:24

Hey Simon-

I have never subscribed to ME, but having seen a few photos of engines from the magazine, I think I have missed a lot of great builds by not being aware of this magazine years ago.

I recall seeing one article about a small engine cast in aluminum in a local magazine, and it was many years ago, and I recall being very interested in the process, but totally ignorant of exactly how it was done.

I have some old foundry books, and the US Naval Foundry Manual, but I have never found a very comprehensive overall guide to modern backyard foundry work and furnaces/burners.

I discovered the resin-bound sand being used by art-iron groups here in the states, and they use cupolas to melt their iron.

I bought a book about how to make a cupola, with the intent of building one, but I could never find a source for coke. Typically the how-to backyard casting books I have seen are not really up to date, and they often don't use the most modern materials and equipment available.

The siphon nozzle oil burner seems to be a somewhat recent development in the backyard casting world.

I have seen a few use salvaged oil-fired heating packaged units used with a furnace, but those combo units are rather large and bulky, since the blower, gear pump, and nozzle are all built into one unit.

The pressure nozzle is very similar to the siphon nozzle, and a pressure nozzle works like a perfume sprayer, and uses hydraulic pressure (about 100 psi) to atomized the air. A small gear pump is used for fuel pressure.

I am currently building a pressure nozzle burner, and will retire my siphon nozzle burners, since the pressure nozzle burner does not require an air compressor, and the gear pump uses a very small fractional horsepower motor.

The resin-bound sand really changes the dynamic of foundry work, and the accuracy of the cast parts is excellent. Patterns are pulled straight out of resin-bound sand using a small automotive slide hammer. Resin bound sand sets into a hardened block of material, and since you do not rap the pattern, there is very little distortion or out of roundness in the molds. Castings made using resin-bound sand are almost the same dimensions as the machined parts, and machining the castings requires just light cleanup cuts on the machined surfaces.

I have never found any information about how to use resin-bound sand, and had to learn it from the art-iron folks. Here is one video I found about someone that made slingshots, that illustrates how resin-bound sand is commonly used to make molds.

https://www.youtube.com/watch?v=EFMXF7szrj4

Bazyle-

I adjust the burner with the crucible in the furnace, since it provides a significant radiant heated area, which helps with fuel combustion.

I use a Morgan Salamander-Super for all my work, but the Super is ferrous-metal-rated, and rated for 2,900F use, and most other cruibles are not rated for that. The Salamander-Super is a clay graphite material.

I use a variety of crucible sizes in both my mini-furnace and my larger furnace.

The mini wil take an A5 (with a pretty tight fit), all the way down to a 0.5.

In my larger furnace, I often use an A10, but it will accept an A30.

I have been told that it is crucial to have more clearance around a crucible for melting iron, but my buddy built a furnace last year, and he has very little clearance around his A10 (perhaps less than an inch), and he easily melts iron. I have come to suspect that the clearance is more about getting the lifting tongs in place without scratching up the furnace interior.

I think the fact that an A-shaped crucible is much smaller at the bottom also automatically gives a lot more space around the crucible for combustion that one may suspect.

For my small furnace, I follow what Noel says, which is about 3/4" clearance minimum around the top of the crucible.

It is always a joy to talk with anyone who has made any castings, professionally or as a hobby, because one can compare notes and methods, and often discover better ways of doing things.

I know of one individual who worked in a steel mill. What a job that would be, and not doubt HOT !

Noel- I heard that Stuart used some form of resin-coated sand that was cured in a hot mold.

Great process for sure. I will check out your album.

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Thanks Noel,

There is a lot of variety in casting methods out there, and many have their reasons for doing it, such as "its fun on a hobby level", etc.

Definitely there is no one way to do things in the foundry world.

I had a few folks offer advice to me early on, but it was impossible to get a concensus about any method or material, and so I was confused for many years, and almost gave up on backyard iron casting completely.

I know of another individual out west who was mentored by a local iron foundry, and he picked it up in a few weeks.

I pass along this information not with the intent of being a "know-it-all", but rather just sharing what I have learned over 8 years.

If I can save just one person some of the grief and failures I had, it will all be worth it.

Hats off to anyone who tries foundry work.

It is my all-time favorite hobby, and I absolutely love it.

It did take a long time to get to the "love-it" phase though.

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Edited By PatJ on 01/07/2022 19:05:58

Gray Iron vs Ductile Iron:

Gray iron is relatively easy to melt and cast successfully, if you pay close attention to details.

I have researched methods for making ductile iron, and I know how to do it (very carefully with special equipment).

I believe I could easily make ductile iron if someone would sell me the nickel-mag additive (Nickel-Mag4).

I have searched the entire US, and nobody will sell a small quantity of that material.

Nickel-mag has to be the correct mix of materials, else you will get a violent explosion, or start a fire that will burn through a crucible and down into the ground. You actually make ductile iron in a lined ladle, not in a crucible.

If anyone has any spare Nickel-Mag4 laying around, please sent it to me.

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So in summary, it is entirely possible to make very high quality gray iron castings in a backyard setting.

The trick is to use high quality consistent scrap gray iron, such as electrical motor end bells, and follow the methods and materials that are used in commercial foundries.

There is no excuse for any defects in any gray iron casting in a backyard setting, if you use high quality materials.

One should never have to put up with hard spots, inclusions, gas holes, overall poor machinability, etc. in gray iron castings. These defects are totally avoidable in all situations.

And you should never have to temper a gray iron casting in order to remove hard spots or make it machinable.

If you have to temper your gray iron castings, you are doing something wrong.

Some temper gray iron to age it, and I do understand that aging iron may be desirable in engine work.

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Green Sand, Petrobond, Resin-Bound Sand, Sodium Silicate Bound Sand:

I have tried all of these sand types, and have settled in on a commercial fine-grained foundry sand called OK85 (made in Oklahoma), and a 3-part resin-binder sytem.

Your foundry sand will either make or break your casting quality, and regardless of anything else, such as the quality of your burner or furnace, if your sand is not right, your castings will be low quality with lots of defects.

Sodium silicate bound sand is what I consider a compromize between the somewhat toxic resin material, and green sand.

Greensand is sand mixed with clay, and sometimes a few other additives such as sea coal, etc.

The beauty of resin-bound sand is that it can produce complex and highly accurate commercial-quality gray iron castings repeatedly and consistently, without problems in the castings.

If you spray on an alcohol-based ceramic mold coat onto the interior of a resin-bound mold, your iron castings will come out of the mold bright and clean, with no surface cleanup required, and a superb smooth surface finish.

Sodium silicate molds can be used with iron (so I am told, I have not tried that).

Most harden the sodium silicate with CO2, and many ruin their cores and molds my overgassing with CO2.

You should gas with CO2 for 5 seconds only.

And most try to compensate for a weak over-gassed core by increaing the amount of sodium silicate, which just exacerbates the problem, and creates a concrete-hard core that is almost impossible to remove.

I think 5% sodium silicate is the maximum amount that should be used.

They do make sodium silicate sytems that have a catalyst, and the catalyst hardens the core/mold without the use of CO2.

The beauty of the resin-bound 3-part resin/hardener/catalyst is that the set time of the sand molds can be varied from 5 minutes to 45 minutes or more.

Drawbacks of the bound sand binders are that the sand can not easily be reused, and with resin-binder, you must wear a commercial chemical-rated respirator.

Petrobond works well with aluminum, but it must be conditioned, since it tends to dry out.

I don't use Petrobond just because I don't want to spend time trying to get it conditioned correctly every time I use it.

With green sand, the pattern is rapped, to break it lose from the mold.

With resin-bound sand, you never rap the pattern, and so the result is castings with very tight tolerances, and dimensions that rival lost-wax castings.

Resin-bound sand is a very deluxe type of core and mold material, and is the most accurate and versatilve molding sand method available. Resin bound sand is quick and easy to use, and works well every time.

The lost wax method is very labor and fuel intensive, and very time consuming, and produces gray iron casting quality only slightly above resin-bound sand molds.

There is a lot of interest in lost PLA 3D printed castings in gray iron these days, but I still say resin-bound sand will produce the same quality or better, with infinitely less time and trouble.

The only thing lost wax castings are really useful for is mass production of numberous tree-mounted wax patterns. For mass production, lost wax is hard to beat.

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Aluminum, Bronze or Cast Iron:

Once you get a good furnace and burner built, and get some good shanks and tongs with sheet metal heat sheilds to protect the gloved hands, then I find gray cast iron to be easier to cast than either aluminum or one of the zinc containing brass/bronzes.

Gray iron does not seem to have any gas issues, and I have never had a gas bubble in any iron casting that I have made.

If you overheat aluminum (I pour aluminum at 1,350 F), you will get all sorts of gas defects.

I have heard you can have gas defects in some brass/bronzes too.

I tried brass and Naval Brass castings, and I must say, those were miserable melts, with all sorts of semi-toxic zinc fumes, etc.

The reason I am making lead-free bearing bronze is that it has almost no zinc in it, and so shoud be easier to pour.

Given a choice, I would pour most engine parts in gray iron as a first choice.

Second choice is 356 aluminum.

If I succeed with the lead-free bearing bronze, then I may like that better than aluminum.

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Edited By PatJ on 01/07/2022 16:30:43

Coated Ceramic Fiber Furnace vs Castable or Plastic Refractory Hot Face:

I prefer a thin castable or plastic refractory hot face (such as Mizzou) that has an excellent resistance to iron splatter.

For my large furnace, I used a 1" thick hot face, and a 2.5" thick insulating fire brick behind that, and then two layers of 1" ceramic blanket wrapped around the entire thing.

The exterior of my furnace is cool to the touch during an iron pour over much of the surface (but not up towards the lid, which gets a bit warm).

Molten iron gets caught up in the combustion air flow, and so will gradually splatter over the interior of an iron furnace. Not really a problem.

The trend it to build furnaces using ceramic blanket lining, which is coated with a high temperature material.

This is a matter of preference in how you like to build a furnace.

My preference is a thin cast refractory hot face, keeping the overall furnace mass as low as possible (to minimize heating times). A cast refractory hot face is very tough and long lasting (if you use Mizzou), and will take a lot of abuse. A cast refractory hot face can easily be patched with plastic refractory.

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Pressurized Fuel Tank vs Non-Pressurized Fuel Tank:

I often see people elevating their fuel tanks, in order to provide a little fuel pressure for fuel flow.

I use a larger fuel tank, perhaps 10 gallons, and there is no way to lift it in the air.

If an elevated fuel tank falls, you can spill oil everywhere.

If you want a burner that never requires adjustment, use a fuel tank that can be pressurized to perhaps 10 psi (with a 15 psi safety valve), and you will always have an exact fuel flow rate regardless of fuel tank level, etc.

I literally never have to adjust my burner, not during startup, not during operation, and no adjustment from melt to melt. I mean I NEVER touch the needle valve.

If an elevated tank works for you, then that is great.

Again it is about what works for your setup.

I can only describe what works very well for me.

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Edited By PatJ on 01/07/2022 16:16:50

Hot or Cold Burner Tube Operation:

One of the most pervasive myths that I have seen online is the thought that the burner tube must operate at a red hot temperature in order to be efficient, or in order to get good vaporization of the fuel (oil).

I call it the "better mouse trap" myth. If someone creates a burner style, and it works well, then they assume that a burner must operate that way in order to work well.

It is a total falacy, but a persistent and prevalent one.

The truth is that there is no need to ever operate a burner tube at a temperature that is not cool to the touch along almost the entire burner tube length.

I have buner tubes that I made 8 years ago, and they operate cool to the touch, and they show no degredation after multiple iron melts.

Any flame impingement on a burner tube should be avoided.

People yell "Yes, but I saw on YouTube....................".

If you saw something related to furnace and oil burner operation on YouTube, you should almost without exception avoid that configuration at all cost.

Another common mistake I see is people allow their burner tube to protrude into the inside of the furnace.

This is poor design.

The burner tube should stop in the tuyere (the opening in the side of the furnace for the burner tube), and be at least 1/2" back from the furnace interior.

Some folks bevel the end of there burner tubes. This is not necesary.

A flat end on the burner tube works perfectly.

Some folks use spin vanes inside the end of the burner tube.

I have tried a number of types of spin vanes, and never found them to be of any use, so I don't use them.

Spin vanes are used in commercial heating units because you are combusting into a large open chamber.

For foundry furnaces, the flames are spinning around the furnace interior, and thus you get a good mixing effect without spin vanes.

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Oxidizing or reducing combustion:

Reducing the fuel amount slightly from its optimal setting will create an oxidizing flame, which means there is a bit of excess oxygen that can react with your metal to create slag.

For melting iron, I increase the fuel flow slightly above the optimum setting, to get about 4" of yellow flame out the furnace lid opening.

This is a reducing flame, and it helps a great deal with minimizing the slag that forms on top of an iron melt.

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Maximizing the furnace interior temperature:

In order to determine the maximum amount of fuel that you can completely combust inside of your furnace, the following method can be used.

1. Start the burner at some nominal fuel flow value, such as 1.5 gal/hr, and adjust for a consistent burn.

2. Allow the furnace interior to come up to red hot temperatures (interior of the furnace is glowing red hot).

3. Increase the fuel flow until yellow flames (this is for oil-fired furnaces) protrude out the lid opening about 4 inches.

4. Increase the combustion air into the furnace (I use a variable speed Toro leaf blower with an additional PVC dump valve) until the flames at the lid are drawn back into the furnace completely.

5. Increase the fuel flow until yellow flames protrude 4" above the lid opening.

6. Increase the combustion air until the flames are drawn back into the furnace.

At some point, you will increase the fuel flow, and then when you increase the combustion air flow, instead of the flames being drawn back into the furnace, the flames will increase in size above the furnace lid.

Reduce the fuel flow slightly, and your furnace is now completely combusting as much fuel as its hot interior surface will allow.

Any significant changes from this fuel flow and combustion air settting will cause the furnace interior temperature to drop from its maximum obtainable level.

For my large furnace, the optimum fuel flow rate is about 2.6 or 2.7 gal/hr of diesel.

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Edited By PatJ on 01/07/2022 15:55:12

Edited By PatJ on 01/07/2022 15:58:35

Drip-style vs Siphon-Nozzle Style Burners:

There is an ardent group of drip-style burner advocates who insist that there is no need for anything other than a drip-style burner. If you are in the drip-style camp, then there is no need to read any further.

I have found drip-style burners to have very poor control, inconsistent regulation, narrow operational range, and often don't burn cleanly during startup or shutdown.

If you like your drip-style burner, more power to you, but there is a much better burner style in my opinion.

I have had several folks demonstrate their drip-style burners to melt cast iron, with perfect results, and all I can say is that if a drip-style burner works for you, and you are happy with how it operates and functions, then there is no need to change burner types.

As will all things foundry, what is important is not that you use my method, or someone else's method, but rather find a method that you like, and a method that works for you.

Backyard casting methods vary widely.

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Edited By PatJ on 01/07/2022 15:46:39

Edited By PatJ on 01/07/2022 15:59:06

Furnace combustion dynamics:

I learned furnace combustion dynamics through observation, and a buddy of mine who was an expert in commercial oil-fired furnaces, later explained to me what was actually happening inside a furnace.

For any given foundry furnace, there is an interior surface area (floor, walls, and lid surfaces).

That total area (say "X" will completely combust "Y" amount of fuel, using "Z" amount of combustion air.

To reach the maximum temperature achievable in a furnace, you need to mix about 14.7 parts air to 1 part fuel.

I studied multiple white papers on atomizing nozzle dynamics, and the types, sizes, and cone spreads that achieve the hottest and most complete combustion.

A Delavan siphon nozzle uses compressed air to atomize the fuel, and it is not a matter of producing the most fine droplets, but a matter of producing a droplet size that burns the hottest.

You can consider a candle flame, where there are hot parts of the flame, and cool parts.

The objective with droplets is to maximize the hottest surface area of every droplet.

Edited By PatJ on 01/07/2022 15:39:42

Edited By PatJ on 01/07/2022 15:59:16

I looked up Luker's posts and casting videos.

Very impressive work from so many repects.

The UK locomotive and stationary engine work is so world class; it is very humbling to see such a level of engine building. Not really something that I see over here.

Here are a few of my thoughts on my backyard casting journey:

I started trying to learn how to cast iron in 2012, and have studied it intensively since then.

I scoured the the internet for information, and found several commercial foundry suppliers who I quizzed about materials.

After several false starts, I settled on a Delavan siphon nozzle burner, pressurized fuel tank, diesel fuel, and a furnace with a thin dense hot face, and low density insulating fire brick as a backer material.

I tried numerous burner types including Ursutz, drip-style, siphon-nozzle, etc.

The Delavan siphon nozzle burner is the Rolls Royce of foundry burners, and with 10 psi on the fuel tank, it operates without the need for adjustment ever. It is highly variable in output across a wide range of fuel flows.

I will share a few observations about your furnace and burner arrangement, with the understanding that everyone has their favorite burner and furnace style/type, and people are often highly resistant to changing their configuration.

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Edited By PatJ on 01/07/2022 15:15:28

I will look up your posts.

I am excited to see others doing foundry work.

I don't want hobby casting to be a lost art, and so I am working overtime to document how I make iron castings, and try and preserve and spread that information with anyone who wants to learn the art of iron.

Fred's work is very impressive, and I have really enjoyed following along with that.

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Edited By PatJ on 01/07/2022 14:34:16

Thanks much for the kind words.

I do use commercial-grade materials, and so I can get commercial grade iron castings.

When I first considered casting iron in the backyard, I was told my many/most that making quality iron castings in the backyard was not possible. I was assured that my castings would have all sorts of defects, gas holes, inclusions, hard spots, etc.

It took me about 6 years to figure out the exact process that has to be used for iron, including a good sand, the right gating layout, pouring techniqes, how to handle the slag, how much 75% ferrosilicon to add, how to handle the radiant heat, and how to coat the molds with ceramic mold coat for a superb surface finish.

I follow John Campbell's 10 rules for good castings, and a few of Bob Puhakka's rules too (which are derived mainly from John's rules).

I can repeately make defect-free gray iron castings that don't need any heat treating or tempering in order to be easy to machine.  One secret to avoid gray iron hardness it to leave the casting in the mold for 24 hours, and let it cool as slowly as possible.  Iron should never be removed quickly from a mold after casting.

I have busted a lot of myths along the road to learning how to cast iron, and I can definitely say that many iron castings I see these days are junk-grade. There is no excuse for making defective iron castings, when you can just make them correctly. I have tried to spread the work, and get others involved in the iron casting process for model engines.

If you know how to cast iron, it is not really much more difficult to cast than aluminum.

One has to use heat shields and such on skimming shanks, and lots of leather protection, since the IR is very high from the hot furnace and crucible surfaces.

Aluminum castings can be made on a relatively casual basis for a minimal amount of money.

To make iron castings, you have to fasten your seatbelt (so to speak), and be extremely religious/consistent about what you do,  and how you do it.

Edited By PatJ on 01/07/2022 14:31:38

Very Good,! with such a small gap between furnace wall and crucible lifting out may be difficult. A4 and A5 will be big enough for most small jobs.

I will probably use an A4 for most melts in this furnace.

The maximum total weight that I would melt in an A4 will probably be 12 lbs, and so it won't take much in the way of lifting tongs. The A5 is a bit tight for iron, but I think would work well for aluminum.

A buddy of mine recently built a furnace, with very little clearance at all around an A10, and it works perfectly with iron, so I think it takes less room than most people think. The hot fire brick walls are very durable, and so no chance damaging them with lifting tongs.

The A30 for my large furnace requires some very hefty tongs indeed, and I have a pouring cart and lifting crane for that. An A30 could hold up to perhaps 80 lbs of iron, so is in a different league as an A4.

Be cautious of using lift out tongs for multi sizes, and the pouring shank needs to be exactly right for the crucible in use. I made a double ended ring shank, the end not in use being the handle.

I have been able to use one set of tongs for more than one crucible size, as long as the tongs fit into the furnace. I have a mechanical stop that I can adjust, and I can adjust the tabs that contact the lower 1/3 of the crucible too, so it can be done, but one has to do it with caution.

For non ferrous I would favour propane - but with fuel cost rising I may have to reconsider that.

I started with propane, and it is quick and easy to use, but with iron melts, the tank tends to lose vapor pressure due to the cooling effect. One problem with propane is that there are just a few places that exchange tanks for a refill, and often the folks working in their work at glacier speed. Diesel is available at almost any gas station, generally 24/7, and cold weather has no effect on my diesel burner down to perhaps 32F. A Delavan siphon nozzle burns very cleanly with diesel, with no smoke, and is extremely controllable, so that is what I use, even for aluminum. If I only melted aluminum, I would use propane only.

Many people seem to judge temperature by eye, iron not so critical but for non ferrous I would counsel it is vital. To that end an inconel sheathed 3mmdia, K type thermocouple is good, without a protective covering it will read fast - OK it will eventually burn out but the speed of reading is more important. A handheld read out is not costly and rules out one of the reasons for failure - wrong temperature.!

I have a MIFCO digital pyrometer, and it works well for aluminum. I think it would work at bronze temperatures too. For iron temperatures, the pyrometers get very expensive, and the tips only last a few melts, so I just judge by eye my iron temps. Iron will start to send out sparks when it reaches pour temperature, which from what I am told is in the 2,400-2,500 F range (from someone who measures his with an iron pyrometer).

For small experimental non ferrous melts a rather smaller furnace and an A3 crucible, gas fired is quick and easy. Using the soft K23 material and ceramic fibre a very light and easily handled unit can be built. I made one using a largeish sievert burner that would run melts of brass in a matter of 10 or 15 minutes.

A buddy of mine recently built a ceramic blanket iron furance, with a high temperature coating, and it works well for iron. I prefer a more robust rigid hot face, which will withstand a lot of long-term iron abuse with only minor patching. For a small amount of money, the coated ceramic blanket is the way to go. For long term iron use, I recommend a high temperature thin hot face such as Mizzou, or 3,800 F plastic refractory.

Are you in the UK ?

I am in the UK-Extended, which is the US (LOL). We are a distant suburb of the UK.

Good Luck Noel.

Thanks much for the thoughtful feedback. I appreciate it.

PS the man to speak to on homemade alloys is Luker- he's here somewhere !

I am going to look up Lurker. I am sure I must have seen some of his work.

Edited By PatJ on 01/07/2022 14:14:51