Editor’s Note: above all, use proper caution and never use wet blocks.
Are Cinder Block Rocket Stoves Dangerous?
Consider the advice of one GardensAll Facebook community member, Chris K., shared that: “Concrete explodes with no warning when it reaches about 3000 degrees. A small fire won’t get anywhere near that temperature, but a large one, or one using a bellows or a fan to increase the draft, can. This is an awesome idea for a small fire, using dry, non-cracked blocks, but it would be safer with stones or clay bricks – or even piled split logs.”
Our issue with this 3000 degrees information is… how can we gauge the temperature that high? What kind of thermometer is needed to measure such a high heat? The closest we could find on is an infrared non-contact measuring device, but it only goes up to 1022 degrees fahrenheit. That wouldn’t be enough to gage a rocket stove temperature for safety.
Looking deeper, thermometers that measure fire are called optical pyrometers, which measure the heat of flames by their color.1)http://webphysics.iupui.edu/warmup/iupui_archive/colorandtemperature.html But, these can be VERY expensive at over $2k, and most people constructing their own cinder block rocket stove are not likely to have one of these in the toolbox.
But a little research should give us an idea of what kind of temperatures we’re dealing with.
For Perspective on Fire Temperatures:
- Campfire temperature average 1571 degrees Fahrenheit (855 Celsius)
- Woodfire ranges 572-1100 degrees Fahrenheit (300-593 Celsius)2))http://classroom.synonym.com/hot-bonfire-8770.html
- Charcoal can create fires typically ranging from 700-1100 degrees Fahrenheit (371-593 Celsius)3)https://www.reference.com/science/temperature-charcoal-burn-be2c8e9041fbc96f#
- Candle flame temperatures average 1832 degrees Fahrenheit (1000 Celsius)
- Bunsen burners can range between 2400-2900, (1352-1593 Celsius)4)https://en.wikipedia.org/wiki/Fire#Flame_temperatures
Is a Cinder Block Rocket Stove Safe or dangerous?
It could be… either one. A car can be dangerous if not handled in the right way, as can a knife, yet we all use these everyday. So whatever we do in life, let’s digest information with common sense and care, and always prioritize safety first.
Our research indicates that the verdict of one chimney builder and a couple engineers is summed up in this excerpt from SurvivalCommonSense.com.5)http://survivalcommonsense.com/build-a-brick-rocket-stove-is-it-safe-to-use-concrete-blocks/
“It would take very intense heat for a concrete block to “explode”. (Think cutting torch temperatures). Over time,they will deteriorate with heat. As mentioned below, the yellow firebrick, or chimney brick, is the only brick to use. They do not absorb heat. Not sure on the cost but it would be money well spent. If you are just occasionally using a rocket stove, you should be ok with regular brick/block.” For more details on this, you can visit this article on SurvivalCommonSense.com.6)http://survivalcommonsense.com/build-a-brick-rocket-stove-is-it-safe-to-use-concrete-blocks/
Wood and charcoal fire temperatures are usually too low for cinder block to combust.
That said, there are people who claim—and show by video if you search YouTube and Google—that it has happened to them. Invariably, there was some degree of moisture involved. So, using dry cinder block with a wood fire should be fine, but there are no guarantees when dealing with volatile substances.
If you plan to build a larger cinder block rocket stove from scratch anyway, why not go ahead and line the inside of of it with firebrick from your local home store? The few extra dollars and extra time will be well worth the insurance that all is well and safe.
Meanwhile, if you’re just going to do a little fire like in this cover image, using a dry cinder block, as best we can determine through research, it’s likely to be safe. The variables seem to be the organic nature of the experiment and how no two scenarios are exactly equal.
We use tempered measuring cups which are made to tolerate boiling water, yet we’ve had one where the bottom cracked right off when we poured in some boiled water. This measuring cup had been used for years without any issue. Perhaps there was some tiny stress already on the glass. We will never know, but the point is when it comes to volatile materials, there are no guarantees.
If you want to proceed, or just get ideas, you will probably enjoy these how-to videos for building a cinder block rocket stove.
DIY Cookstove in Just 5 Minutes
This is super cool… er, super hot, actually! If you haven’t yet jumped on the rocket stove craze, you might wanna grab a few blocks and join in. You can also buy a simple rocket stove such as this one for around $100 dollars.
So whether you’re frugal or just enjoy DIY projects, if you just need a quick backyard cook stove, this super simple home-boy rig is perfect!
This cinder block rocket stove is fueled easily with sticks, twigs and leaves, and it is also wind and rain resistant yet can usually be build for under $10.00!
4-Block Backyard Rocket Stove You Can Try at Home!
This amazing 4 block Rocket Stove is super easy to put together and the only cost is the cost of the 4 cinder blocks. You build it and be cooking on it in just ten minutes or less if you already have some cinder blocks on hand.
Wasn’t that cool?!
Next up is a how-to video for a two burner cinder block stove.
6-Block 2-Burner Rocket Stove
Now are you ready for a six block two burner rocket stove? Check it out and let us know what you think.
Rocket stoves are amongst our most popular topics at GardensAll, so we thought you might be interested in this.
We have another rocket stove article that’s generated a lot of discussion over on the GardensAll Facebook page as to the efficacy of these for greenhouses. Some folks say they can leak fumes that can kill the plants, and others have traded up for gravity feed multi-fuel stoves or pellet stoves.
If you can afford a gravity feed stove, pellet feed or multi-fuel stove for your greenhouse or home, well, that’s awesome, and there are many to choose from. This Wood Burning Cook Stove by La Nordica “Rosa XXL”, with Baking Oven is on our wish list for an inside cook stove and wood burning heater for our future homestead.
Meanwhile, remember, whatever you do and decide, approach it with care and caution.
Disclaimer: We at GardensAll have never done this. Often we are in the role of reporters, researchers, scientists (in conducting our own experiments) and fellow learners on this journey. So here again, we’re sharing something resourceful that’s popular with many people: a quick and easy cinder block rocket stove, since many gardeners are natural DIYers.
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