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.
