Concrete Doodles With Fire!

Concrete art, random doodling, and fire all combined in an activity that is mostly pointless besides being fun. This instructable nearly has it all! The inspiration for this project comes from the early days of the Albany Spin Jam in upstate NY. I have been started that event as a place for fire performers to gather, share ideas, safe practices, and enjoy their art together. One night I took the last bit of fuel and spread it across a strip of bricks laid into concrete. Then I lit it. To our surprise once the flames burned down the remaining flammable liquid was only burning in random spots in the indentations between the bricks and every second or two there would be a pulse of flame shooting between the denser spots of flame creating a mesmerizing visual effect across the grid. A decade later after first trying out some concrete crafts I remembered this effect and decided to try and recreate it with more interesting shapes. I envision creating these slabs to sit around a fire pit would be a fun way to incorporate them into an outdoor space in an area where things are already burning.

A simplified and hopefully factually accurate explanation of how and why the flames act in this way. The liquid fuel runs off the surface into the channels created by the bricks and absorbs into the porous mortar. This creates a steady supply of fuel which releases vapor which is trapped in the channels to readily burn. As it burns down and there is less fuel available the unlit areas will accumulate vapor until it is ignited near a point that is still burning. This ignition creates a pressure wave that pushes the flame along the pathways using up the accumulated vapor thus creating the visual effect we are looking for. The accumulation starts again and this cycle continues until all the fuel is consumed.

WARNING: Fire is dangerous. Only do this outside on a non flammable surface such as concrete, brick, or dirt. Have a fire extinguisher handy and wetting any flammable materials down surrounding the piece.

Materials

Fast setting concrete or cement (CementAll Rapid Set, Quikrete Fast Setting Concrete* etc)

Water

Flammable Liquid (Camp Fuel, denatured alcohol, isopropyl alcohol)

Tools

Bucket Container for Mixing

Tool for Mixing (paddle mixer, mortar hoe, dowel etc)

Large Shallow container to use as mold

Carving/Drawing Implements

*optional large mesh screen, colander, etc*

Squeeze Bottle

Lighter or Matches

Find a spot that you are ok with cement dust settling on and possible drops and bits of mix to fall on. A foldable table you use for crafts works or I often sit on the ground when doing this. Laying cardboard or paper down is an option if you are worried about the surfaces around this area. Once again this is ideally out of doors but can be done safely in a garage or covered spot.

Choose a shallow container like a lid from a storage bin, an old cookie sheet, a round pan, a shallow plastic box or any container you wouldn’t care if it got marked up a bit that is the size you wish to make your slab. I like to reuse and repurpose as much as possible so while you can go purchase something I suggest finding something that would otherwise wind up in the trash.

For carving and drawing implements I once again tend to use found items around my shop. Old screwdrivers or awls work well for doodling in the cement even a smaller diameter round rod will do. For stamping or pressing a shape into the mix a flat strip of metal can make great long straight lines a ring of flat bar stock, a “L” bracket, a thin walled cup, or any simple thin walled shape can work. Stamping allows for larger areas to be created at a faster rate. This becomes more important the larger the slab is since fast setting cement um… sets fast.

If you are using a concrete mix continue to 2A if using a cement mix skip to 2B

2A: if you are using a concrete mix it is necessary to remove the larger aggregate before moving ahead with this process. I find a 5 gallon bucket and a colander are an easy way to separate out the larger chunks of rock and stone. Put the colander in the bucket and pour some mix into it. Then shake and twist until all the smaller particles have fallen through. Dump out what remains and repeat until you have enough sifted material.

2B once you have your mix ready I like to fill my container up to the top if shallow or up a little past the height I want my slab (minimum 1.5 inch or ~4mm to ensure you can make the channels without hitting the bottom). Cement will shrink once mixed and set by 15-25% so that’s why I go a little higher then I want the final piece to be.

2C determining the correct ratio of water to cement is honestly more of an intuitive thing when using it for crafts. The general ratio is 1:4 water to cement but different mixes, humidity, and what you are going to be using it for can all affect how much water is needed. Ideally we want to add as little water as possible to make the cement slightly mold able but not so stiff if is unable to easily spread across the bottom of the container evenly. Too much water will make the slab weak and prone to breaking on removal. I like to choose a container and scoop the dry mix up until it is full then dump that into my mixing bucket. Repeat counting each fill until all the mix is transferred. Then if you had 8 full scoops you’ll want to have two cups worth of water to add once we are ready to begin.

Mix water and Cement and Pour into Container

Put 2/3 of water into mix and stir. Make sure all dry mix is incorporated. If too dry add more water until a firm moldable consistency is reached. Pour into container. Once in the container I shake it up and down and bounce it so the mix flattens evenly across the mold.

Working quickly use your implements to draw your pattern into the cement. Rapids sets in 15 minutes the sifted concrete slightly longer. This is where you can get creative. However try to keep the depth of your marks the same across the whole slab so there aren’t spots where the fuel gathers.

Take the slab to a solid non flammable surface. I suggest using isopropyl or denatured alcohol as the fuel as it’s less aggressive and lets the effect really stand out. A squeeze bottle helps to evenly disperse the fuel over the slab. Once covered using a long lighter or a match dropped from above ignite the fuel and stand back. It will take a minute or so for the flames to burn down and the magic to begin. Blue flames will shoot around the pattern carved into the slab in a mesmerizing way. I just really love the look of this and hope you enjoy it too. Thanks for checking out my pointlessly fun fiery tutorial on an unnecessary project!