Heavy black coating on glass and inside of stove

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Tom Cat

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Feb 27, 2013
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After following the break-in procedure on my new Heatilator insert, I started my first real fire with 4-5 splits. I noticed that there was some coating on the glass since the flame color was very different depending on my angle of view. After 15 minutes of so I lowered the air intake to the lowest setting - It wasn't too cold out so I didn't need a lot of heat and I wanted the fire to last. I also turned the blower on manually.

A few hours later there was a thick black coating over the class and much of the interior of the stove. By thick I mean about the thickness of i piece of paper. It was very difficult to remove from the glass.

My wood has been stacked in a wood shed for about 16 months, so it should be fairly dry.

I'm guessing at this point that maybe I turned the stove down too fast. Any insight is appreciated.

tom
 
Sorry, I posted this in the wrong forum. This is not a classic stove but a new one.

tom
 
Moved to the main forum. It could be the air was turned down too quickly. Running the fan when the stove body is not fully warmed up can also cool down the fire too much. This leads to creosote accumulation. Also, draft is going to be weaker in milder weather. That can contribute to a too slow burn. In general one is better off burning a short hot fire in milder weather and then let the fire go out. Leave the fan on auto so that it doesn't come on unless the stove is hot enough. A short hot fire should burn off most of that black film.
 
If you stacked green wood directly into a shed after splitting I would be surprised if it's seasoned down below 20% moisture unless it was one of the quick drying varieties like ash or pine. Check a freshly split piece with a moisture meter and see what you're working with.
 
Thanks for moving to the right forum.

I think I was too cautious with burning too hot because the manual had warnings all over the place about over firing. I've called the shop to get better instructiions hot how to burn hot without going too hot.

I was told it was "seasoned" when I bought the wood. My intent was to burn it last winter but I never bought the stove so it sat for an extra year. I figured that would be good even if it was not well seasoned. Maybe not. I'll check with a meter next time up up at the house.

tom


tom
 
I highly recommend getting a stovetop thermometer e. g. from Condar or (even better) an IR gun. When I started burning in my insert it took a few weeks before I got my IR gun. Only then did I realize I was burning the insert way too cold. Those modern stoves want to be run between 500 F and 700 F at peak - especially with a full load.

Does the wood when stored in the shed get enough sun and especially wind? Only then will it dry properly. Unfortunately, "seasoned" often means it has been sitting in logs for x months. Of course, wood does not dry while still in logs. It needs to be split and stack to dry.
 
The wood may be fine. This could just be a case of beginner's caution. A thermometer on the stove top will give you some guidance to how it is performing and will help relieve some anxiety about overtiring. When the weather is still mild, but cool enough to burn, start your kindling then add a few 3-4 inch splits on the kindling teepee. (if not top down burning). Let that wood get burning good, then turn down the air, in increments, maybe 5-10 minutes apart. Turn down the air just to the point where the flames get lazy, but don't go out and then wait. Repeat until the flames stay lazy and secondary combustion is robust. Add another log or two in 30 minutes if you want more heat or let the fire finish its course.
 
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Does this philosophy change with a cat stove? I just starting burning in Woodstock ideal steel and have been enjoying the longer shoulder season burn times. However I have quite the coating on the inside of the stove and glass. Is this just something cat stove users deal with when they are burning low and slow?
 
It can be more prevalent with cat stoves running low and slow. Keep an eye on your flue temps and check the flue for accumulation after every cord burned at least until you are more familiar with the stove.
 
My wood shed has sides about half way up, so wood at the bottom doesn't get sun or wind. Wood higher up is exposed to the wind but the roof keeps the sun out.Some of my wood did spend the first summer stacked in the open.

I assume secondary burn refers to flames at the top of the firebox getting air from the tubes across the top. I was getting some secondary burn for a while, but I think it was while the flames at the bottom were out.

In any case it sounds like I need a thermometer so I can heat her up without worrying about causing damage.

I appreciate the advice.

tom
 
Get a magnetic thermometer and an IR gun. I use both. The IR gun is especially useful to get a temperature on the flue collar.
 
I was able to run the stove hotter and the black film is burning up. Some left in the corners of the glass after two weekends of burning. I installed a magnetic thermometer and that has helped with getting it hot before shutting down the air flow. I also checked my wood 11-15% moisture.

Tom
 
Better wood, keep the but ends away from the glass and burn hotter fires. You will get better all the time
 
I had the same issue on my stove and it was because when i shut the air all the way down it smoldered the fire. By leaving my air cracked open just a tad worked wonders and i havent had a problem since. Maybe by putting your stove on the lowest setting you're also smoldering your fire to much.
 
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Tom Cat said:
I was able to run the stove hotter and the black film is burning up. Some left in the corners of the glass after two weekends of burning. I installed a magnetic thermometer and that has helped with getting it hot before shutting down the air flow. I also checked my wood 11-15% moisture.

Tom
Click to expand...
Sounds like things are improving for you. It's a learning process for sure. One question; how are you measuring moisture? 11% seems unusually low.
 
Being that your wood could have a little too much moisture there is some things you can do to compensate.

In these stoves its all about the heat as its the heat in the firebox that allows these stoves to get into the smoke gas burning mode of operation and thats when they burn clean and thats when they really pump out the heat once the secondary flames start up.

Take you some of your good high BTU wood (I use Oak) , splits that are some of your driest and straight grain for easy splitting into kindling.
I split them into like 1" pieces thick with my hatchet. Go to youtube to look at videos of tricks on how to split kindling small and not chop your fingers off.
Some nice ideas there.

Then load your stove up full preferably on a hot bed of coals but leave room some where and thats where a little creativity on load wood comes in as to leave a small space you can lay that small split kindling made of good high BTU wood. I once used like Pine for kindling but small split OAK really heats things up much fast.
Once you lay that kindling on the hot coals you can even throw on one of your firestarters like super cedar or fat wood etc.

You will be amazed how you whole operation of the stove changes when the heat comes up in the stove really quick to over come that little bit of extra moisture in the wood as you can get the temps up to operation levels and then start lowering the input air back down quicker and you will have more of your main wood load left as you havent set there with the door cracked burning up alot of your main wood load just trying to over come that little extra moisture and ending up burning up alot of your main wood load. It can be frustrating for sure.
 
Tom Cat said:
I was able to run the stove hotter and the black film is burning up. Some left in the corners of the glass after two weekends of burning. I installed a magnetic thermometer and that has helped with getting it hot before shutting down the air flow. I also checked my wood 11-15% moisture.

Tom
Click to expand...

If you don't want to wait for the black to burn off or it is being stubborn, you can clean it off manually while the stove is cooled down.

Tip: Conventional window cleaners will not budge the thick black stuff.... When I had that issue a while back I used regular (no-fume) oven cleaner. Worked great.
 
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