Turn Your Traeger Grill Into a Bubbling Cauldron (No Dry Ice)

Want a large bubbling Halloween Cauldron but don't have a big container? You probably DO have a big container if you have a grill. This Instructable shows how to temporarily turn your Traeger Woodridge Pellet Grill into a bubbling cauldron. You can probably turn other grills into a similar cauldron but the modifications will be different.

This project uses an ultrasonic atomizer (pond fogger) to generate the fog. No dry ice, no fog fluid, just water and electricity, and some water ice to keep the electronics cool. See my Water Only Fog Machine Instructable for a discussion of fog generating methods and why ultrasonic atomizers are my preferred fog generating method.

Ultrasonic atomizers are my favorite way to generate fog. For other of my projects using ultrasonic fog generators see: Jack-o-Lantern with fog - no dry ice, Full Size Haunted Cauldron With Fog, Mini Fogging Cauldron - No Dry Ice - No Fog Fluid, Ground-Hugging Fog: NO Chiller - NO Fog Fluid - NO Dry Ice, Real Halloween Fog for Your Desk, and back to my discussion of fog generation in my Bucket based Water Only Fog Machine.

All of these are fun projects are made to be 'fog on demand' and easier to keep going by using ultrasonic atomizers. Ultrasonic atomizers are not cheap, but the price keeps dropping. For the 2025 Halloween season a 12 disc ultrasonic atomizer (pond fogger) including power supply, floats, and extra discs went under $100 on Amazon.

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Traeger Woodridge Pellet Grill (I used the Woodridge Pro model)

12-Disc Ultrasonic Atomizer (Pond Fogger) and Power Supply (fewer discs may be OK, your milage may vary)

3/8-inch Plywood at least 28-15/16 x 11-5/8 inches (Your size may need to be adjusted depending on fit)

Cardboard Sheet or Foam board

Shower Curtain

Aluminum Foil Tape or Duct Tape

2-inch Black Tape (optional - to close the gap between the grill cavity and rail so fog will flow over)

60 x 60 x 15 mm 12V Computer Fan (15 mm thickness is not critical)

Variable 12Vdc Power Supply

2-inch ABS Plastic Drain Pipe, about a foot long

2-inch ABS 60 degree Elbow

2-inch ABS 90 degree Elbow

Glue Gun and Glue Stick

Cardboard or thin foam to protect the shower curtain from the atomizer.

Electrical Tape

Halloween Decorations of your choosing!

You will need to remove all the hand-removeable internal grill parts including all Grates, Drip Tray, Grease Chute, Ember Shield and Heat Baffle. Leave the Grease+Ash Keg in place to catch any water that might leak.

Cut the plywood to fit into bottom of the grill cavity without any gaps. You may need to adjust the dimensions depending on slight variability in grills or if using a different grill. The grill cavity has 3 angled sides with the right-most side being nearly vertical.

The edges of the plywood for the angled sides is cut at an angle so just the top edge of the plywood contacts the grill cavity wall. I made these 3 edge cuts at about a 40 degree angle so that only the top surface of the plywood touches the wall of the grill. That way there won't be a gap for the shower curtain to sag into under the pressure of the water.

I noted that some walls of the grill cavity had bolts protruding through them. Not a big deal for grilling but they certainly could poke a hole in the shower curtain liner. So cover the bolts with cardboard or foam board. I just cut three sheets of cardboard that matched each wall and dropped them into position. They do a great job protecting the shower curtain from damage.

The grill has to hold water, so use the shower curtain to line the grill cavity. I folded the curtain onto itself so that I ended up with 4 thicknesses all around. I did some gift-wrapping style corners in the grill cavity corners to keep the curtain from bunching up.

Make sure that the shower curtain ends up being like a tub with all edges being at the top lip of the grill cavity so that no path exists for water to escape, especially at the corners. If the shower curtain is folded correctly you do not have to rely on any tape joint to keep the water in. The tape only holds the shower curtain in place with its edges above the waterline.

I used the aluminum tape to fasten the curtain to the metal portions of the grill all around the perimeter. I used the aluminum tape because it has very aggressive adhesive and didn't seem to be bothered by the water/moisture.

Fog, especially ultrasonic atomizer fog, needs air added in order to get it to flow out of the container it is located in. I always find a way to add an air source to bring air in to push the fog out. See my Fog Helper Instructable. This project uses an fan driven air pipe over the edge of the grill to add air.

I cut about an inch of black ABS drain pipe off to connect the elbows together. I then cut the remaining portion in to two pieces - one to connect to the fan and the other to extend the tube into the grill cavity. The pipe is press-fit together, no need to glue it.

The 60mm by 60mm fan perfectly lines up with the end of the 2-inch diameter ABS pipe. I hot glued the fan onto the pipe and spliced the power supply output wires onto the fan wires taking care to match polarity; positive to positive, negative to negative.

The fan assembly fits nicely over the edge of the grill cavity in the gap between the grill and the side shelf (when in the folded position).

The fan power supply fits down the same gap between the shelf and the grill. The variable nature of the power supply lets you adjust the fan speed to control the volume of air and the fog flowing over and out of the grill.

I placed the atomizer array on top of some thin foam sheets to insure that any sharp corners on the atomizer would not puncture the shower curtain liner.

The atomizer ends up dumping lots of energy into the water. In order to keep the atomizer electronics cool and prevent it from shutting off due to overheating I place frozen 2-liter bottles of water in the water to keep everything nice and cool. For long run times I just swap out the frozen bottles.

There is a gap between the edge of the grill cavity and an accessory rail. I wanted to make sure that the fog went over the accessory rail so I used some 2-inch black (masking) tape to close the gap off. This is optional.

I added water to just over the top of the black bulbous water level sensor on the atomizer. Make sure the water does not contact your taped edges. You don't want water flowing over the edge of your shower curtain.

You can experiment on what depth of water creates the greatest amount of fog.

I added a skeleton with a glass and fancy cocktail umbrella to the scene along with a large jack-o-lantern.

You are now ready to get spooky!!!! Fire the atomizer up and adjust the fan speed to get the amount of fog flowing that you like. You can even have the grill without the skeleton or even just partially open so spooky fog curls out.

Enjoy!