A newbie with an inherited cast iron stove that scares me

[powlette]

My wife inherited her great-grandparent's antique wood stove. It's marked as Hamilton Stove Co with a patent date of 1905. It weighs about 300lbs. My wife remembers it from her childhood in the early 80's, but we have no idea how old it actually is. It's a family heirloom so I want to use it but I also want to keep it safe. I had it professionally refinished where it was taken apart, glass beaded, nickel plated, paint, caulked, and reassembled. I have attached the before/after photo and I'm really pleased with how it looks. We're using it in our 500 sqft glass greenhouse (photo attached) to supplement the propane furnace as wood is cheaper than gas. Yesterday was our first really cold day and I was impressed that it managed to heat the space to 56F when it was dark and 31F outside so that's great. I put a fan on the side of it to move air around the room and that kept the main body of the stove to about 600F.

I have many concerns though. Part of me thinks her family used this for fifty years without any issue and I probably can't hurt it no matter what I do because I doubt they paid it much mind or even had the tools to monitor it like I do. The other part of me with multiple thermometers including an IR one is watching the base by the embers glow a dull red and read just over 1,000F and worry it's about to shatter in half causing huge damage to itself and it's surroundings. Sometimes he body of it is 300F and I throw in a couple logs and five minutes later it's 800F so it seems really hard to control even with the dampers all the way closed down.

I've read many posts here and I see conflicting answers like some people saying never let it get above 600F and others saying, "mine glows red all day and has for twenty years without issue".

How do I know what a safe operating temperature is for this stove and will something catastrophic happen if I exceed it?

 

[EatenByLimestone]

That’s a beautiful parlor stove! It’ll work much better with coal though.

Glowing red is bad. Decrease the amount of air coming in below the fuel.

 

[Todd]

Beautiful stove! A long time ago I heated a house with a similar stove. It was also designed for coal and I had a hard time burning wood in it until I placed some heavy duty steel plate inside on top of the grates to keep the coals from falling through to the bottom base ash pan. This gave me a little more control and a longer burn time.

 

[begreen]

The stove looks great! Who did the restoration? That's a classy greenhouse too.

If the hottest part stays under 750º it should be ok. Typically this will be at the top near the flue collar. The main thing to avoid is rapid temperature change due something like to spilling water on it. I am a bit concerned about greenhouse use though. That is typically a high-humidity environment which is going to accelerate rusting of the stove. This would be a shame after the nice restoration job.

 

[powlette]

The stove looks great! Who did the restoration? That's a classy greenhouse too.

If the hottest part stays under 750º it should be ok. Typically this will be at the top near the flue collar. The main thing to avoid is rapid temperature change due something like to spilling water on it. I am a bit concerned about greenhouse use though. That is typically a high-humidity environment which is going to accelerate rusting of the stove. This would be a shame after the nice restoration job.

Finding a stove guy was hard. I found a car guy instead. He does classic car restoration so he was able to take it apart and replace fasteners with period-correct ones and get it all cleaned up and painted with high-temp paint. Another company did the nickel plating which was $3500 alone. They told me they'd done many stoves but not one with so much nickel work.

I've found the hottest part of the stove is actually just under the skirt where the hot embers lay up next to the edges. That's where I saw the dull red glow and my IR thermometer read about 1,050F while the top is about 600-700F. I have this nightmare that it's going to crack near the bottom and topple over or spill hot embers on something flammable. I keep telling myself that it was used day in and day out for fifty years and I probably can't hurt it but I just can't shake the feeling that it's going to somehow break. Is that even possible when just burning wood?

Yeah, a lot of people are concerned about humidity but my wife waters each thing by hand - there's no water spraying about. Humidity stays less than 70% in there. There's no mold or anything like that so the stove isn't getting any water on or near it. Here's a view from the inside. The main heat source is a 120k BTU propane Carrier furnace.

 

[mikey]

Nice stove, but buy a efficient clean burning wood stove it will save you money and produce less pollution, Stay away from coal it’s dirty.

 

[powlette]

Nice stove, but buy a efficient clean burning wood stove it will save you money and produce less pollution, Stay away from coal it’s dirty.

Oh thanks! I throw away this 100 year old family heirloom that I put $6k into restoring to save some money on wood.

 

[coaly]

Oh thanks! I throw away this 100 year old family heirloom that I put $6k into restoring to save some money on wood.

If you want to save the stove and prevent damage to it, burn coal. That is the proper fuel since it is primarily a coal stove.

Coal requires lots of air up through it. You only crack the upper air intake for oxygen to get to the top of the fire to ignite coal gas coming out of the fresh fuel. Burning wood in this will burn fast and hot. Many have been destroyed burning wood in them. You will find coal is a steady heat without the temperature spikes.

Wood burns by getting oxygen from anywhere. Close the bottom and open top when fire is established. Only crack bottom to increase temperature. Wood burns best in a wood stove with firebrick bottom on an inch of ash, not elevated or on a grate where it gets to much oxygen, burns too fast and too hot with this grate.

Opening the top secondary inlet designed for coal when burning wood allows a lot of air to rush up the chimney, cooling it, and forming creosote. With a barometric damper and coal you will get much higher efficiency and burn all season until you let it go out.

You will find starting it with wood the temperature spikes, then filling with coal stack temperature will be about 150*f constant. The right fuel makes a huge difference.

 

[powlette]

If you want to save the stove and prevent damage to it, burn coal. That is the proper fuel since it is primarily a coal stove.

Coal requires lots of air up through it. You only crack the upper air intake for oxygen to get to the top of the fire to ignite coal gas coming out of the fresh fuel. Burning wood in this will burn fast and hot. Many have been destroyed burning wood in them. You will find coal is a steady heat without the temperature spikes.

Wood burns by getting oxygen from anywhere. Close the bottom and open top when fire is established. Only crack bottom to increase temperature. Wood burns best in a wood stove with firebrick bottom on an inch of ash, not elevated or on a grate where it gets to much oxygen, burns too fast and too hot with this grate.

Opening the top secondary inlet designed for coal when burning wood allows a lot of air to rush up the chimney, cooling it, and forming creosote. With a barometric damper and coal you will get much higher efficiency and burn all season until you let it go out.

You will find starting it with wood the temperature spikes, then filling with coal stack temperature will be about 150*f constant. The right fuel makes a huge difference.

Thanks for the detailed response about how to do this properly. I'm confused by coal though - coal burns significantly hotter than wood so I don't understand how burning wood could damage this stove if wood burns so much cooler than coal?

My second question is, how would burning wood damage it exactly? Like what would a very hot wood fire do to it exactly and how would I know I'm about to have an issue?

 

[bholler]

Thanks for the detailed response about how to do this properly. I'm confused by coal though - coal burns significantly hotter than wood so I don't understand how burning wood could damage this stove if wood burns so much cooler than coal?

My second question is, how would burning wood damage it exactly? Like what would a very hot wood fire do to it exactly and how would I know I'm about to have an issue?

Coal can burn hotter than wood yes. But in a coal stove with air being fed from underneath wood will burn extremely hot. Do you know if the stove was sealed properly when it was reassembled?

 

[powlette]

Coal can burn hotter than wood yes. But in a coal stove with air being fed from underneath wood will burn extremely hot. Do you know if the stove was sealed properly when it was reassembled?

Yeah, I believe all the seams were caulked. However these is no gasket around the bottom door, but it fits so tightly that I'm not sure it matters because with the door closed as well as the dampers on the bottom, the fire goes out in short order which makes me think it's not letting any air in from the bottom. I also shined a light inside around the seams and could not see it outside so that seems to confirm.

Everyone in my wife's family who ever used this stove is now gone and it sat and fell into disrepair for ~15 years so I don't know much else about it or how it was used other than my wife's childhood memories from 40 years ago. I can run to tractor supply and get some coal for it, but if air is coming up from the bottom will it burn at 3000F and break? This is all why I'm so worried about it and my wife will be distraught if something goes wrong. We appreciate your guidance.

 

[bholler]

Yeah, I believe all the seams were caulked. However these is no gasket around the bottom door, but it fits so tightly that I'm not sure it matters because with the door closed as well as the dampers on the bottom, the fire goes out in short order which makes me think it's not letting any air in from the bottom. I also shined a light inside around the seams and could not see it outside so that seems to confirm.

Everyone in my wife's family who ever used this stove is now gone and it sat and fell into disrepair for ~15 years so I don't know much else about it or how it was used other than my wife's childhood memories from 40 years ago. I can run to tractor supply and get some coal for it, but if air is coming up from the bottom will it burn at 3000F and break? This is all why I'm so worried about it and my wife will be distraught if something goes wrong. We appreciate your guidance.

No the stove is designed to run coal. Coal needs air from underneath.

 

[powlette]

No the stove is designed to run coal. Coal needs air from underneath.

Okay but let's say I throw some coal in there and get it going and a seam isn't properly caulked or the door used to have a gasket or something and air is coming in from the bottom. Then what? Is there any way to know that it's safe to do this? I'm just picturing a pile of coal burning at 3000F and melting my family heirloom.

 

[bholler]

Okay but let's say I throw some coal in there and get it going and a seam isn't properly caulked or the door used to have a gasket or something and air is coming in from the bottom. Then what? Is there any way to know that it's safe to do this? I'm just picturing a pile of coal burning at 3000F and melting my family heirloom.

I will let coaly answer that. He is much more experienced with coal than me and much better at explaining things as well

 

[begreen]

Coal stoves need air under the coals to keep them burning. It is slower burning at a hotter ignition point. You regulate the burn by the air feed wheels at the lower part of the stove. It will burn slowly and steadily once you have the hang of it. The right size of coal is important too, but that is coaly's dept. to advise.

Wood has a lower ignition temperature and will get too hot all at once when bottom-fed with air. This is what you are experiencing. A wood stove feeds the air on top of the wood instead of below it.

 

[coaly]

The coal burns as a red glow on the grate. The more air you give it, the more blue flames you will see on top. It will not get hotter than with wood. There are more BTU’s in a pound of coal than wood, but you aren’t burning it near as fast, so those BTU’s are stretched out over time. Closing the air on the bottom will make a coal fire glow, or go out. It is much more controllable than wood.

Chose the coal size that will not fall through grate openings. Probably Chestnut size. The larger the coal pieces, the more air between them, so the faster they burn. You get the same btu per pound out of all hard coal, the size changes the speed it burns. Smaller pieces have less space for oxygen, so burn slower. You use coal from a bin, so you can shovel the larger pieces from the top on colder days, and use the fines around the bottom when less heat is needed for a slower burning fire. Just like using larger or smaller pieces of wood to control how much heat to expect.

When you start a wood fire, don’t let it burn down to coals and expect coal put on top to ignite. It doesn’t ignite and get hotter as it starts. The wood burning freely is much hotter than coal. You’re confused about the fire temperature. The coal you put in does not all burn at once for all the heat available in it within a few hours like wood. It will be burning in the morning, into the next day, so the time element stretches the btu output over two to three times the duration, measuring a lower temperature for a longer period of time. You will put your hands on the pipe where you can’t touch it with wood. That is the efficiency difference. No smoke to form creosote, so chimney temperature can be very cool. Normally 100 to 150*f compared to 300* with wood. Yet the stove will be the same temperature.

When starting a wood fire for coal, only use small kindling. Put a sprinkle of coal on it. Light it, keeping the fire bright and hot. You want the flames ripping up through the coal. Slowly add more coal as you cover the fire, you will see it glow red from the bottom, but look dark with no flames on top. It is strange the first time covering a fire with black rocks, but the air will go up through it. You may have to open bottom door to get enough air to start the coal. It takes lots of air, unlike wood. Once going you will cut the air back.
Never poke a coal fire from the top. That will kill it. Looking up from under grate, you will see the glow get bigger across the grate. When established, (this takes 10 to 15 minutes after doing it a few times-the first time it may take an hour to get the hang of it) slowly pour coal over the fire to cover it. It will slowly work it’s way up, not igniting all at once. Coal is very slow to respond, not like wood. Everything you do can take 10 or15 minutes to see the difference.

Once established, for overnight you will learn how much to fill by pouring through the top. Normally to top of burn pot.

You won’t have to shake the grate to clean the ash that forms under the fire much the first day. When you can no longer see red glow looking up through the bottom, shake a little until red glowing coals drop. A quick jerking motion knocks the ash loose the best. There are different ways to shake it down. You will soon learn long wide strokes dumps ash fast when there is an inch or so of it. If only a little ash is present from burning lower, shorter quick strokes are all that is necessary.

The most important thing with a coal stove is emptying the ash daily if you think it needs it or not. You never want the ash to build up to the bottom of grates. This blocks the air that keeps grates cool. The number one issue with coal stoves is warped or melted grates. It is not dangerous, they no longer shake and clean properly.

When you get good at cleaning a coal fire, after shaking about 1/2 hour, you may notice dark spots on the grate looking up from the bottom. That is where a slight cleaning with poker, or thin rod can clean the ash from the slots that are not open. It’s all about an even steady glow. It doesn’t burn with flames like a fireball like wood.

Finally, when you learn how deep the coal should be, you learn how each stove needs to be stoked. That’s putting coal on, or pouring from a coal hod through lid. By shoveling into a horseshoe shape with it thicker around sides, you end up with a shallow spot in the middle. This is where a small blue flame should be present as a pilot light to ignite coal gas as it is expelled from the deeper areas. If you hump it up in the middle, it will take a long time to burn up through the pile to ignite on top. This is when you will smell sulfur outside, and lighting the gases in the stove adds more heat. You will learn to always carry a flame at the lowest point of coal bed. It sounds confusing, but it’s simple once you do it a few times.

Boilers are trickier keeping the horseshoe deep around the sides to protect side sheets from expansion, plus moving down the tracks shakes the fire keeping it clean, when you may not want it, and opening the throttle too much can lift the fire putting burning cinders and embers right out the stack. Once you fire locomotives, stationary fires are much easier and very relaxing. You won’t get enough draft without inducing air with a blower to melt anything.

 

[mikey]

I didn’t say throw it away I only pointed out that are environmental issues with burning coal, those issues not only affect the environment as a whole but also the air quality in your home.

 

[powlette]

@coaly I really appreciate your detailed reply here. I ordered some coal which is coming later today. I'll try it out and report back!

 

[powlette]

@coaly I bought some nut coal and it's working great. It's just like you said - a consistent burn that's not too hot. This is a game changer for me as adding wood every hour over night wasn't an option. I really appreciate you taking the time to write that detailed response to me. It looks like a couple hundred dollars of coal will save me a couple thousand dollars of propane.

 

[stoveliker]

Nice to see that old beauty being functional!

 

[bholler]

@coaly I bought some nut coal and it's working great. It's just like you said - a consistent burn that's not too hot. This is a game changer for me as adding wood every hour over night wasn't an option. I really appreciate you taking the time to write that detailed response to me. It looks like a couple hundred dollars of coal will save me a couple thousand dollars of propane.

View attachment 302904

Glad it worked out well for you. Those old stoves really were designed pretty well to burn coal. And make horrible woodstoves. I knew coaly would walk you through it very well.

 

[coaly]

Good. Told you it would be controllable and not have a melt down. Coal can only do that when a blower is forcing air through it such as in a forge.

That fire looks quite heavy, unless you’re bringing the temperature up with it burning hard. You can turn it down to only a tiny glow from the bottom on warm days and not lose the fire. It comes with practice. You will find coal is a lot less work. It does have nasty emissions, and makes a lot of ash that isn’t useable like lime from wood. It doesn’t hurt the soil, but it doesn’t do it any good. I use it around poles or fences where I don’t want weeds to grow.

Not everyone gets a coal fire established the first time they try it. The biggest mistake is thinking they have to burn wood down to coals before putting coal on. When you do it right you will have glowing coal quickly. Just strange covering a good fire with rocks thinking this is going to kill it! My coal grate is much larger and only light it once a year. Never lost the fire yet. If you ever lose the critical mass of the fire, no matter what you do you are going to lose it. It can’t recover once it hits a certain point.

The next mistake is thinking the fire will respond right away. Sometimes you just have to walk away and find it grows by itself without playing with it. Worst case scenario is let the ash door open for maximum air flow to get it going. Use caution doing this and stay with it. This expels lots of gas from the coal on top and when you close the ash door it will ignite the gases on top. It won’t burn right with ash door open because of getting too much dilution air. These are the things you’ll learn by doing.

You will find when letting it burn overnight, you may think it is almost out. A little shake and you should see some glow from the bottom up. Notice I always state to look at the fire from bottom of grate. When you get the hang of it you will be able to tell a rough fire from a smooth even one from the top, but the even glow from bottom tells the story.

The reason coal gets a bad rap from being dirty is the ash is finer and can become fly ash becoming airborne easily. Try to only shake when the draft is strong. You may have to shake a little first to kick it up and get the chimney hotter. Then later shake it the rest of the way until you see coals start to drop. This allows the stronger draft to vacuum the flyash up the stack instead of drifting inside.
Finally, at season end let it burn out. Only shake, don’t add anymore. Mine takes 3 days after no longer adding coal. Then empty ash and clean chimney very, very well. The fly ash in chimney is acidic. At least the longer it’s in there, the more neutral it becomes. I remove inside pipe and run water with garden hose through it, rinsing clean until the smell is gone. Then brush chimney with a poly brush or Soot-Eater. I prefer the Soot Eater. Then wrap rag around brush and do it again. I clean with a wet rag the same way. I have even put drain oil on a rag and run it in the flue to coat it for the summer. If you don’t rinse the inside black pipe, it will pinhole in a year or so.

The last word of caution is if you get large chunks of what looks like molten lava that won’t burn, that is a clinker. It can come from user error, usually poor coal, or some stoves are more susceptible to forming them. You can only remove it from the top. I have only formed them in large locomotive boilers, never my coal stove. You will find not all coal is equal. What burns fine on one style grate may give problems with another. Then sometimes what comes from a good breaker changes as they hit different veins underground looking like shale that won’t burn right. About the time you think you have it mastered, you find another trick that works better.

 

[bholler]

Good. Told you it would be controllable and not have a melt down. Coal can only do that when a blower is forcing air through it such as in a forge.

That fire looks quite heavy, unless you’re bringing the temperature up with it burning hard. You can turn it down to only a tiny glow from the bottom on warm days and not lose the fire. It comes with practice. You will find coal is a lot less work. It does have nasty emissions, and makes a lot of ash that isn’t useable like lime from wood. It doesn’t hurt the soil, but it doesn’t do it any good. I use it around poles or fences where I don’t want weeds to grow.

Not everyone gets a coal fire established the first time they try it. The biggest mistake is thinking they have to burn wood down to coals before putting coal on. When you do it right you will have glowing coal quickly. Just strange covering a good fire with rocks thinking this is going to kill it! My coal grate is much larger and only light it once a year. Never lost the fire yet. If you ever lose the critical mass of the fire, no matter what you do you are going to lose it. It can’t recover once it hits a certain point.

The next mistake is thinking the fire will respond right away. Sometimes you just have to walk away and find it grows by itself without playing with it. Worst case scenario is let the ash door open for maximum air flow to get it going. Use caution doing this and stay with it. This expels lots of gas from the coal on top and when you close the ash door it will ignite the gases on top. It won’t burn right with ash door open because of getting too much dilution air. These are the things you’ll learn by doing.

You will find when letting it burn overnight, you may think it is almost out. A little shake and you should see some glow from the bottom up. Notice I always state to look at the fire from bottom of grate. When you get the hang of it you will be able to tell a rough fire from a smooth even one from the top, but the even glow from bottom tells the story.

The reason coal gets a bad rap from being dirty is the ash is finer and can become fly ash becoming airborne easily. Try to only shake when the draft is strong. You may have to shake a little first to kick it up and get the chimney hotter. Then later shake it the rest of the way until you see coals start to drop. This allows the stronger draft to vacuum the flyash up the stack instead of drifting inside.
Finally, at season end let it burn out. Only shake, don’t add anymore. Mine takes 3 days after no longer adding coal. Then empty ash and clean chimney very, very well. The fly ash in chimney is acidic. At least the longer it’s in there, the more neutral it becomes. I remove inside pipe and run water with garden hose through it, rinsing clean until the smell is gone. Then brush chimney with a poly brush or Soot-Eater. I prefer the Soot Eater. Then wrap rag around brush and do it again. I clean with a wet rag the same way. I have even put drain oil on a rag and run it in the flue to coat it for the summer. If you don’t rinse the inside black pipe, it will pinhole in a year or so.

The last word of caution is if you get large chunks of what looks like molten lava that won’t burn, that is a clinker. It can come from user error, usually poor coal, or some stoves are more susceptible to forming them. You can only remove it from the top. I have only formed them in large locomotive boilers, never my coal stove. You will find not all coal is equal. What burns fine on one style grate may give problems with another. Then sometimes what comes from a good breaker changes as they hit different veins underground looking like shale that won’t burn right. About the time you think you have it mastered, you find another trick that works better.

I have found that matchlight charcoal works really well for starting coal as well. A couple years ago lots of customers had coal that was really a pain to light for some reason. The charcoal worked a little better for me then.

I also spray down stainless liners chimneys connector pipes and the stove interior with wd40

 

[dznam]

I

I also spray down stainless liners chimneys connector pipes and the stove interior with wd40

Edited, I found the answer as to "why" in Coaly's post, above.

 

[dznam]

Good. Told you it would be controllable and not have a melt down. Coal can only do that when a blower is forcing air through it such as in a forge.

That fire looks quite heavy, unless you’re bringing the temperature up with it burning hard. You can turn it down to only a tiny glow from the bottom on warm days and not lose the fire. It comes with practice. You will find coal is a lot less work. It does have nasty emissions, and makes a lot of ash that isn’t useable like lime from wood. It doesn’t hurt the soil, but it doesn’t do it any good. I use it around poles or fences where I don’t want weeds to grow.

Not everyone gets a coal fire established the first time they try it. The biggest mistake is thinking they have to burn wood down to coals before putting coal on. When you do it right you will have glowing coal quickly. Just strange covering a good fire with rocks thinking this is going to kill it! My coal grate is much larger and only light it once a year. Never lost the fire yet. If you ever lose the critical mass of the fire, no matter what you do you are going to lose it. It can’t recover once it hits a certain point.

The next mistake is thinking the fire will respond right away. Sometimes you just have to walk away and find it grows by itself without playing with it. Worst case scenario is let the ash door open for maximum air flow to get it going. Use caution doing this and stay with it. This expels lots of gas from the coal on top and when you close the ash door it will ignite the gases on top. It won’t burn right with ash door open because of getting too much dilution air. These are the things you’ll learn by doing.

You will find when letting it burn overnight, you may think it is almost out. A little shake and you should see some glow from the bottom up. Notice I always state to look at the fire from bottom of grate. When you get the hang of it you will be able to tell a rough fire from a smooth even one from the top, but the even glow from bottom tells the story.

The reason coal gets a bad rap from being dirty is the ash is finer and can become fly ash becoming airborne easily. Try to only shake when the draft is strong. You may have to shake a little first to kick it up and get the chimney hotter. Then later shake it the rest of the way until you see coals start to drop. This allows the stronger draft to vacuum the flyash up the stack instead of drifting inside.
Finally, at season end let it burn out. Only shake, don’t add anymore. Mine takes 3 days after no longer adding coal. Then empty ash and clean chimney very, very well. The fly ash in chimney is acidic. At least the longer it’s in there, the more neutral it becomes. I remove inside pipe and run water with garden hose through it, rinsing clean until the smell is gone. Then brush chimney with a poly brush or Soot-Eater. I prefer the Soot Eater. Then wrap rag around brush and do it again. I clean with a wet rag the same way. I have even put drain oil on a rag and run it in the flue to coat it for the summer. If you don’t rinse the inside black pipe, it will pinhole in a year or so.

The last word of caution is if you get large chunks of what looks like molten lava that won’t burn, that is a clinker. It can come from user error, usually poor coal, or some stoves are more susceptible to forming them. You can only remove it from the top. I have only formed them in large locomotive boilers, never my coal stove. You will find not all coal is equal. What burns fine on one style grate may give problems with another. Then sometimes what comes from a good breaker changes as they hit different veins underground looking like shale that won’t burn right. About the time you think you have it mastered, you find another trick that works better.

Excellent posts, Coaly! Makes me think about getting a coal stove...