Introduction: Fire Snakes in Liquid Sand Gas Fire!

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Since you are here reading this instructable you are clearly interested in learning the secrets of the fire swamp so that you can live comfortably for quite some time. This guide will help you make the dreaded lightning sand and the dangerous flame spurt and who knows if you are out in your garage there might even be some ROUS's so keep your wits about you.

The title of this instructable is a literal mouthful but I am going to cover all three experiments that you can easily do with this setup it so that if you want to make any of these projects this instructable is a one-stop-shop! The reason why there are three things in one is that it is possible to do them all with the same set-up by making small adjustments and planning ahead with you material selection to ensure it can withstand the effects of each of the different experiments.

After watching Mark Rober's liquid sand video and the follow up done by The King of Random for how to make the smaller Liquid Sand setup it really made me want to build one for myself. However as what often happens once the seed of an idea is planted in my brain it starts to branch out into all sorts of possibilities. So if you are pumping a gas through sand to make a fluidized bed my brain thought what other gases could be used and how would that change the potential such as swapping out the air for propane? This sounded really great to be able to have one of those fancy outdoor gas fire pits that you can make yourself.

NOTE: When you are making something that uses propane you have to be VERY CAREFUL. Also be aware that propane is a heavier than air gas so it has the potential to remain settled in the sand you are using.

The first decision was to swap our the PVC that has been used for matrix of tube that spread the gas through the sand for something that could handle some heat yet still be easy to work with so I settled on 1/2" copper pipe. One of the major benefits of burying the gas supply matrix is that the flames are insulated away from the pipe which protects the copper from warping or becoming brittle when used as an outdoor fire pit.

This does not let me off the safety hook though before I could begin to use this project I had to test every solder connection for leaks and use Teflon tape rated for gas application on every threaded connection. With all of these factors taken into a account and tested I still thought it prudent to get a regulator with an extra long 12' hose.

Now wait where is this giant fire snake?!? I know that you came here to see how to make your Tremors, Dune, or space fan film a reality using sugar and baking soda in time lapse for your worms. So if you are actually reading this instructable and not just looking at the pictures you can see we get to that experiment once the build is complete and fully tested as an outdoor fire pit.

I do not know to what stage you are going to take this project but here is what you are going to need to make it happen.

I want to reiterate that this project involves dangerous potential from the soldering process and its fumes to the powerful potential of compressed air to the explosive potential of propane. If you intend on repeating this project be careful and take proper precautions and seek help from skilled persons if needed.

Note: The purpose of each tool is listed with the tool to help you make substitutions if you do not have that tool.

FTC Disclaimer: I earn a percentage of the sales through the affiliate links provided through Amazon.




  • Tape Measure (Measuring the pipes)
  • Pipe Cutter (Cutting the Pipes)
  • Hammer (Used with metal punch for starting drill holes and to encourage the pipes and fittings together)
  • Metal Punch (Used to start the holes in the copper pipe and the roasting pan)
  • Marker (Helpful to remember where you measured)
  • Sand paper (Roughing up the copper surfaces for soldering
  • Drill (Drilling things?)
  • ~3/64" bit to drill the Air Output holes. (I had started with a 1/32" bit which I quickly broke so 3/64's it is!)
  • 5/8" bit Step Drill Bit (Used to make the holes for the pipes to pass through in the roasting pan)
  • Caulk Gun
  • Torch (Used for soldering and lighting)
  • Plumbing Solder (Used for soldering)
  • Plumbing Flux (Used for Soldering)
  • Safety Glasses (Used for soldering and testing. Be sure you get ones that fit!)
  • Leather Gloves (Using for pipe cutting and soldering)
  • Something 1/4" tall to help with marking the pipe for drilling ( I used left over plywood)
  • Drill Press Vice (Holding the pipe while drilling and soldering)
  • 5 Gallon Bucket (Used to mix the Sugar Snake mixture)

Step 1: Acquire Your Materials and Cut Your Pipe

With the exception of the propane regulator I was able to get all of my components from a nearby hardware store or other local sources but the internet can also be a great resource. The hardest thing was finding a suitable container to put the project into. I knew I wanted this to hold fire which meant that plastic was out of the question, but finding a reasonably priced, safe metal container with good dimensions took some time.

Note: I planed on using a galvanized steel tub for this project but there are inherent dangers to using galvanized metal for projects that are exposed to high temperatures especially for long periods of time. If you check out this link to the American Galvanizers association it recommends keeping the temperature at or below 200C or about 400F. The purpose of this is to keep the zinc coating from oxidizing and coming off to be inhaled by those around it causing lung irritation and a condition called metal fume fever.

I settled on a rectangular enameled oven roasting pan since it is designed to withstand heat yet is still light and readily available. There are many stores that sell them new but I ended up finding a deal and buying one used from a secondhand store.

One other option is if you are wanting this to be a more permanent installation you could just build this into a brick enclosure if you are wanting a fire pit which would likely remove the need to an under pan or you could go with something more sturdy like steel.

Now that we have the boilerplate conversations about safety and materials handled if you have been able to acquire your materials and collect your tools it is time to start measuring and cutting your piping. Using a pipe cutting tool takes a little bit of practice but once you make your first few cuts you will really get a handle on it. So if you are using a similar sized container to me here are the pieces that you will need to cut.

It is likely that you will not have the same size container as me so should you decide to make it you will need measure your dimensions and you might might need more or less of the same materials.

My Roasting Pan allowed be to have six 14.5" sections across the pan all told here are six sections I cut for the project.

  • Six 14.5" Sections for the gas release tubes
  • Ten 1" Sections for connecting the Tees (The Tees end up practically touching)
  • Two 3" Sections for routing the pipe out of the container (These come off the matrix and pass through the whole we will drill into the pan)
  • Two 6.5" Sections for bringing the pipe to the final Tee (These connect as a seventh tube that spans the length of the pan on the outside to bring it together for the connector to our gas source)
  • One 2" Section to connect the Threaded Copper Coupler

All told this came out to about 2" short of 10' so if your Roasting Pan is similar size to mine you should be in good shape to get only one 10' section of copper tube. Using the pipe cutter is something you get the hang of pretty quickly. It is a balance of tightening the rollers and spinning the tool so that the rollers are tight enough to keep the blade in place and continue pushing the pipe into the cutting wheel but not so tight that the tool gets stuck and you need to back it off. I found it easiest to spin the pipe cutter in the direction like you are trying to continually trying to hook the pipe cutter onto the pipe like a clothes hanger which had me rotating the tightening handle the direction of the closed side of the tool.

The part that I deliberated the most about was the propane regulator. I did not want to spend a bunch of money but at the same time I wanted something safer so that meant a longer hose and I wanted something that would be versatile for other projects. The conclusion that I came to was to get an adjustable 0-30 PSI regulator with a gauge to try and help with control and repeatability with a 12' hose attached to help me keep my distance or at least let my propane tank keep its distance.

Step 2: Mark and Drill Your Holes

Following the designs that Mark Rober and The King of Random made we are going to be putting a whole legion of holes into our 14.5" sections of copper pipe at 90 degree angles.

The first step is to draw a line to guide your holes so that they are positioned at 90 degree angles from each other. Since I am using 1/2" copper pipe this is easily done by laying a 1/4" board onto a table and then using that as a guide to draw your first line, see the first and second picture. Then rotating the pipe 90 degrees so the line that you just drew is pointing straight down into the table and using the board as a guide to draw the other line. See the third picture. Once you have all of the lines drawn on your 6 pipes you are ready to start marking up where the holes need to be drilled.

I then used the same board to make a template for where I wanted my outlet holes to be located. Now my tubes are not even inch measurements so I ended up marking one inch segments from each end and when I got to the middle I had 2.5" left in the middle with ideally two more holes to drill. I ended up spacing them 0.75" from the last hole making the final spacing in the middle 1". That said there is no hard and fast rule and you can adjust your holes at the ends as well. My measured template can be seen in the fifth picture.

Then I used a hammer and a punch to start the holes on the metal tube. The purpose of this is to keep my drill from walking all over the place since I do not have a drill press and I do not want my drill bit to break. You can see the indents from the punch in the sixth picture.

I went with a 3/64" drill bit which is about 1.2mm heavily choked up in combination with drill press vice to hold the pipe in place as you can see in the seventh picture. I had started with 1/32" which is about 0.8mm but that did not last long because in spite of the pre-indenting the holes and choking up the bit I still broke this bit after only 5 holes. Make sure that you choke up on the bit if you are using a standard hand drill to reduce the length of the bit subjected to the sheer force of poor placement. You maybe thinking where do I get a bit that small since most drill bit sets only go down to 1/16"? You will need to go online to get these smaller bits or if your nearby hardware store sells Dremel brand or high speed rotary tools they might have a bit set that goes down this small for a reasonable price which is what I did.

All told I drilled a total of 168 holes and I am glad my drill, drill bit, and my back survived! The final product looks like the eighth picture.

Step 3: Solder the Main Assembly to Go Into the Tub

This step is where I put the "earned" in learned because I learned a lot through my mistakes soldering pipe and how to put a project like this together which could common in handy if I even wanted to make a towel warming rack for my wife. I am going to do my best to pass the learnings from my mistakes along to you so that you do not make the same mistakes that I did to make you build process easier, better, and cleaner than mine. So what were my mistakes? I soldered the Tees to each of my 14.5" tubes separately instead of building the frame out progressively adding pieces to the main body. You can see if this in the third picture.

First you are going to need to clean up your pipe ends and inside your fittings. Take your sand paper and rough-up/clean the ends of the pipes and the inside of the fittings. There are a lot of connections here so this will likely take you a while like it did for me. If you have a wire brush that can fit in the fittings that will save your fingers a little bit. (Note: I did not have a wire brush so I learned that I want one for future projects)

With all of your pipes and fittings cleaned and ready it is time to start soldering. Now my advice is to start from the farthest point out and then work towards where we will pass through the wall of the roasting pan and then to the final connector. So this means you would be able to answer the question, "What has a 14.5" copper pipe, two elbows, soldering flux, solder, and a blow torch .... "This person!"

Starting with the two elbows and a 14.5" section of pipe with the holes drilled into it apply a thin coat of flux to the two ends of the pipe and slide on the elbow fittings. Make sure you take note of what directions the holes point because this sets the orientation for the rest of the project. I then used my work bench and pressed the pipe on the surface to ensure that the elbows where pointing in the same direction and not off at angles. Next with the pipe positioned so it will not burn anything start heating up one of the elbows with the blow torch trying to have the tip of the flame touching the pipe because that is the hottest part. The flux will heat up and melt away cleaning the pipe as it does. After the pipe has had a chance to heat up it will likely start changing colors to be a little iridescent which means it is getting almost hot enough to melt the solder. Then coming in from the opposite side of the pipe and fitting from the flame which should represent the coldest part of the joint touch the solder lightly to the point where the pipe and elbow meet. It should melt quickly and get pulled into the joint if the metal is hot enough, but if it is not then pull the solder away and continue heating. Soldering these joints does not take much solder so be sure to have a light touch with the solder once it starts to melt otherwise you will end up with a few extra globs of solder bunching up at your joints like I did. With your first elbow done carefully using your leather gloves or a pliers flip your pipe over and attach the other elbow in the same way making sure that is is still perfectly lined up with the first elbow and the holes. See the first and second pictures.

Now as that first pipe with the elbows cools you can prepare the next rung of the configuration by applying flux to the ends of another 14.5" pipe and covering two 1" sections of pipe with flux. Connect these five pieces together to make an H shape making sure that the holes in this next section will line up with the hole on the section you previously soldered (See the third picture). The section with the elbows is likely to still be hot so be careful and use leather gloves or wait for it to cool. Now with this H shaped sub-section still loose but coated in flux carefully press the exposed sections of the 1" connecting pipe into the open ends of the elbows. If the pipes are still hot it is likely that the flux with start to melt and run which is fine. With the two sub-sections together start at one end and solder the three connections that you made: The 1" pipe to the elbow connect, the 1" pipe to the Tee connector, and lastly the 14.5" pipe to the Tee connector. Once that is complete flip it over and do the same to the other three connections on the other end of the setup again being careful because the pipe will be hot.

With these steps laid out of adding another wrung to the system continue to do this four more times using up your 14.5" sections of pipe. Building this out like this starting at one end and working your way to the other will give you a lot of flexibility to make sure that everything fits. Since I did not do this I had to reheat, melt solder, and manipulate a lot of my connections to get everything to fit which took a lot of extra time and put a lot more heat stress on the copper. If you encounter a 14.5" pipe that is so long that it does not fit the others simply cut off the needed length with the pipe cutter.

Note: Do not solder the 3" section to the last Tee quite yet we will get to that in the next step.

Hopefully your assembly looks better than mine in the fourth picture because you applied the advice I gave you about building it one piece at a time.

Now with the piping complete like what you see in the fifth picture use the piping to mark out where the holes will be for piping to exit the roasting pan about 3/4" up from the bottom of the pan so that we can move onto the next step.

Step 4: Drill Holes in the Tub and Finish Soldering

Now that the holes are marked in the tub using the pipe assembly we just finished constructing we can drill through the tub wall using the Step Drill bit making it just a little bit larger than the piping so I am targeting a 5/8" hole, but that turned out to be a pipe dream. Using the hammer and metal punch I started my holes by hanging the roasting pan over a protruding 2"x4" on my work bench. I also used this 2"x4" location to drill the holes. See the second picture.

Note: The step drill bit was a great tool and very helpful even though I had never used one before. My holes did not line up perfectly so I had to use the step drill bit to make them into more ovals that circles which was very easy to do.

With the holes drilled I tested the fit, see the third picture, to make sure that whole piping circuit fits well. After the fit is confirmed I pulled the setup out of the tub and apply flux the pipe and solder the 3" extensions that you see in the fourth picture. Then I waited for it to cool to put it back into the tub.

The last few bits of soldering are to take the two 6" sections of pipe, the two remaining elbows, and the last tee connector. First flux the connections and place it onto the setup as shown in the fifth picture. Remember that once these connections are soldered our pipe assembly and the pan will be merged together so be sure to double check your connections to make sure that you are satisfied with all of your connections up to this point. See the fifth picture.

Once you are satisfied go through the soldering process for these last few connections leaving the last soldering connection of the threaded copper cup as you can see in the sixth picture. Flux the 2" extension and solder these connections at which point we can put the soldering equipment away and break out our wrenches and Teflon tape for the steps of putting together our gas tubes. See the sixth picture.

Note: It is very important to let the copper cup cool before trying to thread in your brass coupler with Teflon tape!

Step 5: Teflon Tape and Tighten All of the Threaded Connections and Apply the Fire Barrier

With the soldering completed we can move onto the threaded connections. I waited until the copper piping was cool to the touch before attaching these threaded connections because I did not want to chance exposing the Teflon tape to the latent heat from soldering.

Starting with the 1/2" to 1/4" brass coupler apply the Teflon tape wrapping in the same direction as the thread and then tighten it into the Copper Cup. See the first picture.

Insert and tighten the ball valve into the reduced end of the brass coupler. The valve that I found had a male end on one end and a female end on the other which saved me from having to buy a male to male coupler. Also the valve had a sealant already applied to the male end of the valve meaning that Teflon tape would not be needed.

After the valve is installed apply Teflon tape to the male universal adapter and screw this into the female end of the valve. I went with a standard universal air fitting so that I would easily connect and disconnect my source from this project and it would also be pressure rated. It is very important to use a brass fitting for this since steel has the potential to spark which would not be good if you are using it with propane. See pictures two through four.

On the propane sourcing side using the 3/8" flare to 1/4" coupler with Teflon tape on only the 1/4" side screw the regulator tube, coupler, and female adapter together. It is important to not use Teflon tape on flared fittings. See pictures five through seven.

With all of the piping finished it is time to seal up the tub. If you are only planning on using it for a fluidized bed feed with compressed air or nitrogen then you can use whatever caulk you want but since my intended use involves fire I am using a fire barrier rated caulk to ensure that it does not breakdown should the copper pipe or roasting pan get hot enough to conduct heat to the caulk. See the eighth picture.

One other small addition I made was using a 0.75" section of copper tub to prop up the far side of the piping to try and have it all be a consistent height in the pan. See the ninth picture.

The final result can be seen in the tenth picture which I left overnight to allow the fire barrier caulking to to cure and become less tacky. Also it let the anticipation build before testing because what is a good project without some anticipation?

Step 6: Test As a Sand Fire Pit

With the whole configuration all set up and the fire barrier caulk cured it is time to test out the Sand Fire Pit. I purchased a 50lb bag of playground sand and poured it into the pan spreading it evenly over the piping ensuring that there was even cover with enough material so that it will insulate and protect the pipe and allow for the propane to diffuse through the medium to arrive at the surface.

The way that I tested this system for the first time and the method that I used to light it the subsequent times is as follows.

  • Attache the regulator to the Propane Tank
  • Position the propane tank 8' - 10' from the roasting pan
  • Start with all three valves closed (Tank Valve, Regulator Valve, and Valve at the Pan)
  • Attach the air connectors between the Regulator hose and the roasting pan
  • Open the propane tank valve
  • Slowly open the regulator valve until the gauge reads about 1 PSI
  • With a partner located at the propane tank to shut it off if needed move over to the roasting pan
  • Light your ignition source of lighter or torch and slowly open the valve on the pan. You should hear a slow hiss of gas as it passes through the valve and enters the pan. If you regulator is set to a low and safe enough level there should be no disturbance in the sand and the propane that percolates through should quickly catch fire.
  • Now back up and enjoy

I use the valve on the regulator to shut the system off to try and allow the regulator hose to empty out as well.

I found that very little propane is needed to have a very impressive yellow flame. You maybe able to turn the gas up a little bit but I would not recommend going too far as it increases the potential of the sand being blown out of the pan creating a mess and also exposing your copper supply pipe. I never turned the regulator up past 0.5 to 1.0 PSI to get impressive flames. The pictures attached where taken with probably between 0.5 to 0.75 PSI from the regulator.

Note: Once the gas is flowing through the system my gauge zeroed out so all of my PSI reading are based on the gauge before I opened the valve at the roasting pan.

This process is a great test for the the system's ability to handle fire and to give a practical experience for how much gas flow is needed to create a satisfying flame. The goal is to build intuition for the sugar snake experiment which we are moving to next!

If you end up using this as a guide to make your own outdoor fire pit it would be great to seem a picture of your setup in the comments.

Step 7: Giant Fire Snake Test!

Time for the main event the giant sugar snake fire pit!

With you play sand in place in the roasting pan it is time to mix the sugar snake concoction. We will need to mix a 1:4 mixture of baking soda and sugar that is well mixed. I am going to be by mixing 5lbs of baking soda with 20lbs of sugar in a 5 gallon bucket before I pour it into the roasting pan on top of the play sand.

There are a number of things that I learned through this process. Here is a distilled list of what I learned through experimentation.

  • There is a size limit to this reaction. Trying to get a sugar snake that is larger that about 8"-12" in diameter will result in a small black blob that does not grow beyond a few inches tall. This is could be because the reaction that creates the carbon foam of the sugar snake has a limited amount of force it can exert and since most of the reaction take place around the perimeter of the snake which grows linearly with the radius while the cross sectional area grows by the square of the radius which means the ratio of circumference to cross sectional area gets worse the larger the radius. So each little bit of reaction is expected to carry more weight which results in the our sugar snake turning into a sugar stump.
  • Piling the sugar and baking soda into a cone. This helps to feed the reaction at the perimeter as the sugar and baking soda are consumed by having the the mixture further up the cone avalanche down into the primary area of the reaction.
  • Applying enough flame is important. Some of the tests that I ran I tried turning down the propane source so that the flames only existed around the started snake. This however resulted in extreme slow or no growth of the snake causing it to stall out as well.
  • Clean the area around the snake before lighting it. After running a number of experiments and swapping out sugar and baking soda mixture I was not able to get all of it every time so that where little pockets of the mixture around the primary pile. In general this should not be a problem but what had a tendency to happen is that these smaller side snakes would bond with the larger central snake and weigh it down slowly or stopping its growth as eventual dead weight.
  • It takes a long time. Since these snakes are much larger they grow at a much slower rate so it will take many minutes to get past the initial growth to get to examples of some of the larger snakes I show in the pictures which took about 20 minutes.
  • Do this outside in a clear area away from fire hazards. This project involves the extended burning of propane which releases carbon monoxide and carbon dioxide which can be very dangerous in closed unventilated spaces.
  • Sugar snakes grow fastest under moderate amounts of stress. Since I was doing this experiment outside there were occasional gusts of wind which caused the snake to shift a little bit exposing more sugar and baking soda to the flame which accelerated the conversion to carbon due to the combination of increase oxygen and exposure. While I did not try it having a small fan nearby could be helpful for accelerating the growth.

All told it was a really fun project to make and fun experiment to perform. Let me know if you end up making a sugar snake demonstration yourself and what you learn in the process.

Check out my youtube video for more of this demonstration!

Step 8: Test the Tub As a Fluidized Sand Bed (Future Project)

While performing a liquid sand demonstration was the impetus of this whole project I am a little tool limited at this moment and I have been unable to procure a good source of non-flammable compressed gas to test out the liquid sand aspect of this project.

I will be sure to update this section of the instructable once I has successfully tested this application but I am confident that it will work once I have a suitable regulator and source of air.