I will apologize at the forefront for the poor pictures, feel free to contact me with any questions.
Step 1: Step 1 - Gather Your Supplies
A pair of urns, pots, cauldrons, etc... - We had an extra pair sitting in the yard that I commandeered for the sake of the haunt
2"x2" 's - A total of 3 were used for our 1'x'1'x1' cube bases
Wood Screws/Drill or Screwdriver/Wood glue - Had these laying around
Luan or any other type of thin plywood- Home Depot is right down the street
PBA or PVC pipe - we used 4' of 2" per urn
PBA or PVC 90deg coupler - choose same size as pipe and only one is needed per urn
Harbor Freight Pond Light- Look for these on sale.... and any colored submersible light will work
Hole saw kit - Harbor freight
Drill - the bigger the better depending on urn material
Fog machine- we have used everything from 400-2000w units with this design
Ice... ice... and more ice (enough to fill each urn, pot, etc to 3/4 full plus some spare ice for the rest of the night)
Step 2: Step 2- Construction
For my large urns, I was lucky to have a 1'x1' square base, despite their 32" height. But... this is where it really pays to overbuild the base, instead of assuming it will be strong enough. So I proceeded to make a 1'x1'x1' cube (consisting of 4 pieces of 2"x2"x12" and 8 at 2":x2"x9" -since 2x2's are really 1.5x1.5). These were all glued together with water resistant wood glue, attached with 3" wood screws, and then had squares of the luan attached to 5 of the sides with the bottom left open.
Find exact center of the top skin of this box and drill a hole large enough to fit your chosen pvc/pba through. Then choose one of the side faces and repeat this process.
Paint the entire cube (both inside and out as it will be around a large source of moisture). And we want this to last for many years... right? Of course!
Try to either match or compliment the urn so it looks like we planned it this way. :D
Now the fun part.... if your urns are resin, like mine were... you will be drilling through the thickest portion of the material and will have to use water to keep the bit cool. So since I was using 2" pba (looks like black pvc) I decided to use a 2.5" hole saw to give me a bit of wiggle room and the ability for the water to drain out as the ice melts.
Now, cut 1' of your chosen pipe material, and push this through the side hole in the base. Once inside, attach the 90 degree coupler, and do the same with the rest of your pipe through the top hole of the base. You should be left with a cube with a portion of pipe sticking out one side and the remainder sticking vertically.
Slide the urn over this, so that the pipe exits the newly drilled hole in the base of it. Arent you glad we left some wiggle room to make this easier? I sure was!
Now, if you're lucky you will not have to cut the pipe at this point.... but if you are left with pipe sticking above the bottom 1/3 of the urn... you will have to cut it down so that only 1-2 inches are visible (as per the photo).
Step 3: Step - 3 the Revenge of the Step... or Finishing Touches
Great question random haunter reading this instructable! I shall not leave you hanging any longer....
Final touches are incredibly simple, and I wish I had pictures to give it justice (but it honestly looks like a bubbling cauldron in person... and everyone thinks its dry ice, and yet it is safe for the little trick-or-treaters to touch!)... but back on track.
If you purchased the harbor freight lights (as I did) assemble these as per the instructions and choose your desired colored lens. I choose red, but green makes for a great potion/toxic look. (these must be used with water or ice though as they will melt if left un submerged)...
Stick this on the base of the urn and aim it straight up (you can drill a hole and pass the cord through the bottom or just toss it over the side as I did since the black cord doesn't show up at night.
Before turning it on, fill the urn/cauldron/pot/wheelbarrow... etc... with ice until it is 75-100% full.
Now... the fun begins...
Grab your fogger (please make sure it is filled with fluid before you use it) and the goal here is to allign it with the side pipe coming out of the base cube. And leave atleast 1" of room between the nozzle and the pipe. (this side of the urn/base should be facing away from your viewers - the photo below is from the house facing the street and you can see their placement).
Turn it on and set it to constantly fog (for cheap foggers, just rubber band or tape down the switch so that it will start fogging immediately each time it warms up).
Lastly plug in the light and enjoy.
The individual photos of the urns below are without ice, thus it floats straight up... which still looks interesting... but the shot of the pair is with the ice added and it drapes down the urns and looks fantastic in person. If I can ever find any more photos I will add them to these.
Feel free to comment and let me know how this worked out for you and if you have any questions at all!