Oversized Foam Jack-o Lantern

As a kid, I was driven by a house that had used a ball shaped plastic septic tank as a Jack-o Lantern. It was amazing to an 8 year old. I always wanted one when I could decorate my home myself. Well this year, Home Depot came out with this really cool pumpkin stacks that were 8 feet tall. But they were super hard to find as everyone wanted them, sort of like the 12 foot skeleton a few years ago. So.... I decided to make one fulfilling my childhood goal after 30 years. I only got the top one done. I have no idea how I am supposed to stack these things. At second glance of the website, I guess the whole stack was 8 feet tall, not just the single pumpkin. Who knew? But I digress. Here is a painfully detailed picture heavy look at how you too can created your own giant Jack-o Lantern if you wanted to, maybe even fulfilling a childhood dream of your own.

Supplies

Tools:

Hot wire cutter: make your own or buy

Hot wire knife - Harbor freight

Chainsaw - not needed but helpful

Curry comb - to shave down the foam

80 grit sand paper

shop vac or dust collector - I vacuumed up 5 contractor bags full of foam beads/ dust

Hand saw and a sharp knife

Air compressor: to get the foam dust off the sculpture as you work.

Paint equipment: I sprayed, rolled, and brushed on paint

flour sifter - to get chunks out of the sand as you reuse it.

Plastic sheeting - for under the foam to catch the sand, paint spray, glue drips, or whatever

webbing straps to hold the foam together when gluing

Tape measure - there were a lot of angle cuts

Bamboo skewers - to hold the foam pieces when glued.

****Safety Gear****

chain saw gear if you use a chain saw

Safety Glasses when using spray foam or sanding foam (the dust hurts your eyes. Ask me how I know)

Nitrile gloves for glue and paint

Hearing protection if you are spraying with a loud HVLP sprayer

Materials:

Foam Blocks - Free from Tractor Supply or any trailer retailer.

Spray foam - I used and like Great Stuff Pro spray foam

Glue - Needs to be waterproof so I used Titebond II. Elmers glue will re-activate and run.

Sand - Any sand will work but Playsand is really consistent and nice to work with plus it is cheap

Paint - Exterior rated paints. Bright orange shades are hard to make. They take a very deep yellow base.

Frosted Shower curtain - to block out behind the carved face.

LED flicker bulbs - amazon

cheap stretchy spider webs for goo

My best guess is I spent 450 to 500 dollars on the build for materials and about 30 days of time in the evenings and on weekends when I wasn't working my day job. Most of the money was in glue, paint, and spray foam.

Step 1: Styrofoam Blocks

The pumpkin is made out of styrofoam. I have approximately 135 blocks of styrofoam in the build. I got them free, yes free, from Tractor Supply. They get blocks of foam in as packing material between trailers that are stacked up when they ship them. The blocks are 12x12x18 or 19 inches long. They have to throw them away when they are done shipping them to the stores. Most stores stack them up on pallets and whoever wants them can have them.

I have found that during the past year the price of foam has tripled. As such, some of the stores are now sending back the blocks instead of giving them away. Many are not as most of the foam is damaged due to the weight on the trailers being stacked on them and the tie straps used to secure everything. So ask and see if they are saving them or sending them back.

If you can't find foam for free at a local Tractor Supply store, you can also check:

• Trailer companies that resell
• Construction companies that may sell compression foam cheap that they didn't use due to a plan change
• Foam distributors for Billets of foam. These will be full cost
• Craigslist or Facebook marketplace.
• And if you live around an ocean, the marinas have them often for dock blocking.

I source building materials where ever I can. I got lucky and found 150 blocks of foam over 3 months this year at a local Tractor Supply.

Step 2: Cutting the Rings

With a structure this size, you can't just start gluing blocks together and then shape it the way you want. You have to plan out how to get the most out of your foam blocks, with minimal waste, and good solid surfaces to adhere the foam to. I used a Segmented Bowl Calculator for turning wooden bowls I found online. I scaled down my dimensions to fit from feet to inches in their calculator. So an 18 inch block which is 1.5 feet became 1.5 inches. I could then calculate how many blocks I needed to make an 8 foot circle, what angle each side needed cut to, and how much that meant I needed to cut off the ends. Math, lots of math or is it maths... hmm.

The problem though is that even with the math, cutting foam with a homemade hot wire cutter works well but doesn't give you a true flat cut. The wire heats up and sags which causes it to wave a bit as it pulls through the foam creating a not so flat edge. They are darn close but off just enough that you end up with some gaps and a 12 degree angle you need may be 10 or 15 depending on which way the wire moved.

I dry fit all of the pieces with a nylon ratchet type strap that used to hold a kayak on my truck. This let me see how close or far off I was on the angles. I cut several filler pieces on the smallest circles to try and widen the circle by about 3 inches as it was just a bit too small. This messed up every other angle as circles on set angles don't like to be widened.

Every cut off pieces as long as it wasn't crushed due to a bad block of foam was saved for later to glue back on.

You can cut foam in a variety of ways but cutting through a 12 inch block of foam eliminates most of those options. If I had a giant bandsaw, I could have gotten extremely smooth clean cuts but I don't own somethings that large so a hot wire cutter it is. I did make a jig to hold the blocks steady and I could cut clean angles then using the edges of my jig. It worked extremely well for this application. You can see it in the previous step in the photo with the crushed block.

Step 3: Gluing With Spray Foam

I swear as i was looking at the foam rings I heard someone on a loudspeaker say Locking In Chevron 1. I mean they do look like the start of a great Stargate SG1 build. Anyway.... back to the pumpkin

The rings were all pre-cut and pre-fit to make sure they would line up. And wouldn't you know it, sometimes even doing that, I had gaps to fix. I used the deck on the back of my house with plastic laid down to do the glue ups. This allowed for a completely flat ring to be created so I knew they would stack up great when I had to glue the rings to each other later.

Great Stuff spray foam is an amazing glue for EPS (White Bead Foam). The Pro version has a gun the foam filled can attaches to and allows you to spray it on very controlled for gluing surfaces and seams. I would never try to do this with the disposable cans and straws. The control with the gun and the ability to leave the can attached for weeks if I want to is amazing. Yes the cans are more expensive but the foam is also a different quality and it stretches way further than you think as you use it.

The rings were ratchet strapped into place while they dried under minimal pressure on the straps, just enough to hold the outsides in line. Bamboo skewers were used to hold the pieces square or pull in sides as needed. They are removed as soon as the foam dries, in less than an hour.

The excess foam is then cut off with a small hand saw. At that point you flip it over and fill any gap you see to strengthen the joints. Then cut off the excess again.

I nearly got myself in trouble here. I glued up the 8 foot ring and I had 8 feet 1 inch to get it off the porch over the rail. I was so close that I had to turn it to get away from the points as they hit the posts and I couldn't get it past. Close but I made it.

Step 4: Changing the Original Shape

You know when you plan something out in your head and then you step back and look at it and you are like man what was I thinking? Yeah, this was that moment. I had 8 rings made up. 2 each at 8 feet, 7 feet, 6 feet, and 5 feet. If I put them together the way I wanted I would have had an 8 foot ball. But then I started to think about how most pumpkins look. Unless you get one of the decorative mini ones, they are not a perfectly round ball. I had made an orange, not a pumpkin. So now what? They are cut and glued. And I had 4 rings glued together already. The 8 foot, 8 foot, 7 foot and 6 foot rings were glued up for the center. Flipping those so the 6 foot was down still didn't look right.

So... I took the remaining 6 foot ring, cut it into 4 sections and added extra fill in blocks making it 6 and a half feet. This would now be my new base with the 7 foot ring on top. But what about that extra bottom ring that was 5 foot? Well I set both 5 foot rings on top and man did it look funny. I started to build out the 5 foot rings with some new blocks I cut in triangles in 6"x15". This left lots of odd triangle gaps which I had to fill in with scrap pieces of foam.

But I now had the basic shape of a pumpkin that didn't look like an orange and sort of tapered how I wanted it, more gourd like but still pumpkin-ish.

Step 5: Using the Cut Offs

I used almost every angle cut off piece I had from the ends of the blocks. Some rings had 1 layer and some had 2 layers of cut offs reattached. Each was cut as close to the angle as I could get and foamed into place. A lot of compound angles to get the outer structure slopes to line up where I could carve them into a smooth finish. I went through several cans of spray foam and used hundreds of skewers plus some painters tape to hold pieces together while it dried.

Nothing was shaped smooth yet as I needed flat surfaces to attach the cut off pieces to. It is really difficult to add a flat block to a rounded surface so for the moment the pumpkin looks like something out of Minecraft.

The 8 foot center rings got the large triangle cut offs from the 5 foot rings attached. With 17 blocks total making up the 8 foot ring, this made 8 wide points and one flatter face area for ridges on the pumpkin.

The pumpkin at this point is 3 large pieces, the bottom 2 foot section, middle 4 foot section, and top 2 foot section with hundreds of pieces making up the shape.

Step 6: Forming the Basic Shape

Carving foam takes time and a lot of energy. The larger pieces you can remove at the beginning, the less time you have to spend shaping and sanding. I used a hot wire cutter, a hot knife, and a hand saw to carve in the 8 main ridges of the pumpkin. I kept the pumpkin together to do the shaping so all 3 sections would line up with each other.

At this point, I added wax paper between the lower two layers and sprayed foam in to fill the gaps left by my cut off pieces not lining up exactly with the next layer. This kept the layers separate (the wax paper) but allowed me to fill it in to make it look much smoother and closer to being one giant piece vs two distinct layers.

Step 7: Curry Comb and Vacuuming the Yard

So a typical day in September and October for my family is vacuuming the yard. Doesn't everyone do this? I guess not....

When you carve with a curry comb, it makes a giant mess. I swept up 5 contractor bags full of foam beads and dust from carving the basic shape of the pumpkin. I had my kids help me as much as they could trying to keep ahead of it. It legitimately looks like it snowed in my yard as I work so you have to sweep it up often or the wind makes a snow drift in your neighbors yard. I may have paid my children for their help. I mean they are 7 and 9 and they have needs like Pokemon Go poke-balls or fortnite skins.... so you want 5 bucks? Come vacuum the yard.

There isn't anything fancy here when it come to shaping, just working your forearms until you have to wear wrist braces because they hurt so much as you slowly shape the foam down to a nice pumpkin shape, getting rid of all the flat surfaces. But you do get to look like a snowman for a while so there is that. It is literally just hours of slowly removing everything that isn't a pumpkin.

Step 8: Filling Gaps and Sanding

Sanding is very different than the curry comb. The curry comb shapes the foam and these nice big beads of foam cover everything. Sanded foam is tiny particles that stick to everything, don't come off well, make your face itchy, and gets in your eyes no matter what you do. Sanding foam is not fun. My kids posed for the picture but sanded less than 2 minutes as they also thought sanding foam was not fun. Wear gloves when you do this as the 80 grit sand paper will slowly eat your finger prints and your hands will be rough and hurt a lot. I wore through a good pair of leather gloves after a few hours of sanding.

As you sand, you find all the spots where the spray foam didn't fill in the gaps. You either see them or feel the foam flex under the sand paper. This is where you add a ton of spray foam in all the little gaps, trying to make a solid surface. Then you walk around the both directions and you see all the other gaps you missed. And you do this for several days as you sand because you just keep finding gaps. Then you think you are all done and start coating everything in glue and you find more gaps.... I am getting ahead of myself. First we have to carve the face.

Step 9: Carving a Face and Access Door

Since I was making the top pumpkin from the pumpkin stack from Home depot, I used a projector and projected the face onto my carved shape. I used a sharpie, a big one at that, to outline the face. But 3D objects and 2D projections don't line up well. They are close but you have to modify it to make it work so after the project was done, I fixed the edges and eyes to make the 3D shape look better.

Now I had to carve it. Well my hot knife maxes at 5 inches for depth, and that is with removing the depth guard. The foam is between 12 and 15 inches thick where it was built up. The hot wire cutter doesn't work like this. It makes straight flat cuts. My sawzall maxes at about 8 to 9 inches depending on the blade. So.... chainsaw it is. The hot knife was used first to get the shape partly cut in. Then the chainsaw was used to plunge cut close to where I wanted to be. I am not an expert chainsaw carver so I got close to the edges but didn't only carve with a saw. Fun fact, the foam beads will stick to the hot chainsaw muffler and give it a nice white melted coating. It chips off pretty easy.

After the chunks were knocked out, I used a hand saw and the hot knife to finish the cuts and try to smooth it out the best I could. I couldn't access the inside yet so a door had to come in soon or I wouldn't be able to finish the teeth. Then I noticed how close the eyes were cut to the edge of the foam. 1 inch on one side and 3 inches on the other. This was a weak point that was going to break if I wasn't careful. So, 3/4 inch plywood to the rescue. A pocket was cut over each weak, point and the plywood glued in with spray foam.

At about this point, I cut an access door in the back of the pumpkin so I could get inside to work and add lights later. I cut it about 2 foot by 2 foot angling the chainsaw in a bit so it would but be a straight cut you could see through. My kid fit inside perfect. I struggled to get through the opening as when i angled in the blade, it narrowed the opening to about 16 inches wide. I wish someone would have told me that the width goes down when you add an angle. Math or is it Maths......

Step 10: Shaping the Lid and Stem

Since the top section of the pumpkin was off already to fix the eye weak points, I decided it was time to make the top. I didn't want the top to fit on perfect. The end goal was for it to look like it was being lifted off. I created the basic block shape and used a marker to outline where the ridges were for the pumpkin sides. I used a hot wire cutter to get the outline and then turned the cutter at an angle and cut the bottom like you would see a knife cut on a pumpkin lid. The top was also cut down with the hot wire cutter a bit to get the angle started.

When I changed the 5 foot section from the bottom to the top in my design, I didn't need the center to be angled in so much so I had cut out an 8 inch thick circle from the middle. This gave me a great stem shape that I was able to reuse. I glued it on the top with spray foam.

The whole thing was then carved down the the curry comb and sand paper to get the shape I needed. The stem was carved with the hot knife melting in lines to look like ridges of a pumpkin stem.

I drilled a hole into the lid and into the top section and added 1 1/4 in PVC into a 45 degree elbow. This allows the lid to stay up at an angle and hopefully look like it is being lifted off by a 12 foot skeleton when the display comes together.

Step 11: Plastic Wood and More Spray Foam

Remember those gaps I kept finding? Well I found more and kept filling them with spray foam. I turned most of the sections upside down at least once and I would see more gaps to fill. Again, I had to cut off the excess and sand smooth.

Knowing that the pumpkin face is where most people will focus their attention, I wanted to make sure I had the seams of foam hidden as well as possible. I also wanted to reinforce the teeth and carved sections of eyes/ nose just a bit as well. That is where people are likely to touch if they just want to know what it feels like or how it is made. I have learned it is a reaction most people do without thinking, so protecting it from chipping away is a priority.

To get the seams a bit smoother and protected, I used Plastic Wood. When i got the first container (32 oz), it was pink as there is drydex in it which shows you when it is dry as it turns brown. I don't really need that but I thought, hey, it won't hurt anything. When I went back to buy the other 3 containers I needed to finish, I found I can get the version without drydex for 12 dollars instead of 17. Although it made my daughter sad to not have a pink pumpkin, I saved 15 dollars and got the non drydex plastic wood for the teeth and remaining face. I used a glove and just smeared the plastic wood into the seams and followed up with a wet brush to smooth out some. Then I decided it was too thick, so I mixed in some water to make it paintable and used a brush to paint on the rest.

Step 12: Hard Coating With Sand and Glue

When I built a giant skeleton last year, I found that Elmers glue all is not as waterproof as they say. So this year I switched to Titebond II which is water resistant, but also very much more yellow than the elmers glue. I paint on the glue with a roller and chip brush if needed and then throw play sand on it. This sticks to the wet glue and when it dries it makes a cheap hard coat that is bump resistant and also little kid fingers resistant to pulling out chunks of bead foam. Once painted it is very waterproof. Sections that didn't get paint actually got mushy after 2 days of rain, just FYI.

You have to do it in small sections as the glue will tack up and dry. As you throw the sand, drips of glue, beads of foam, leaves, and all kinds of other random stuff will get into the sand. I use a flour sifter to filter out the chunks every so often so I don't end up with random junk stuck in the surface of the pumpkin.

I used 2.5 gallons of Titebond II to coat the whole pumpkin. I had 150 pounds of play sand that got used over and over. There might be 50 pounds actually stuck to the pumpkin. The rest is in my shoes, drug through the house, and is the bane of my wife's existence this past month as she finds it everywhere. Actually I am not sure if she hates the sand or the foam beads more at this point.

Step 13: Primer and Base Paint

I had about 2 gallons of paint left from last year when I made the skeleton so I used that as a primer on the whole pumpkin. I sprayed a thick coat on to coat all the sand as it absorbs in the most on the first coat. I then added some yellow and orange and tan from old project paints to make enough paint for a second primer coat. As these were older cans, they had rust on the rims and I had to filter all of the paint to get it to spray well. I used an old HVLP gun I have had for the last dozen years and it was used when I got it. It is finicky but when it works, it does a great job.

After the primer coats had dried, I painted the orange top coats. It took two coats or about 1.5 gallons to cover the whole thing.

Step 14: Subtle Paint Colors

I have found very few pumpkins that are actually completely one color of orange. Usually they have speckles or areas of green, darker shades of orange, and lighter shades of yellows on ridges. So to not have a very orange pumpkin that looks completely fake, I added colors. I hit all the recessed areas in a slightly deeper shade of orange. and the ridges in some watered down yellow with a sea sponge. When I painted the stem green with the sponge, I rinsed most of the green out and then flicked it hard at the pumpkin so it would splatter little specks of green everywhere. I also used the sponge to add some green shading in spots kind of like dry brushing to give it some life.

The cuts for the carved face were a golden rod yellow and some misting of orange speckles to tone it down a bit.

I then went back on the stem and added some dark brown/blackish mis-tint paint I bought to add a 3rd color. I left the light tan color in the deep cracks and crevices to make it look like the stem was starting to dry out.

Step 15: Shower Curtain and Flicker Bulbs

You cannot have a Jack-o Lantern without having it lit up. I bought 2 full size flicker LED bulbs and put them inside. It looked great except that you could see all of the foam blocks and spray foam seams. So to resolve this, I got a clear shower curtain and use bamboo skewers to hold it in place. Clear shower curtains are more translucent instead of clear which diffuses the light perfectly allowing you to see the glow but not the blocks.

Step 16: Carving Knife

A giant pumpkin had to be carved with something so.... the super cheap carving knife you used to get in that pumpkin carving kit.... well here is a 7 foot version of the carving knife. Made of foam again, hard coated and painted. The blade is a material called Palight which is a Foamed PVC Sheet. It cuts nice on a table saw and band saw, is flexible, and holds up well. It is about 1/4 inch thick and I got it from a local sign shop. They print big signs on them for events.

I drew out the design based on a picture of the cheap carving kit knife. I used a band saw to cut out the blade teeth and a chop saw to finish them as I couldn't fit it into the band saw for the cross cuts.

The blade was painted with an automotive base primer and then I used a Jewelers Rub and Buff silver paste to get it to shine like metal.

Step 17: Pumpkin Seeds and Goo

The goo is just the really cheap stretchy cotton or poly webs you get in a bag. I added some orange paint and squished it all together then laid it out on a cardboard sheet to dry.

The seeds are foam, just hand carved / shaped down with a curry comb from scrap pieces. I did hard coat these with plastic wood to smooth them out some and then painted them an off white.

This is honestly my favorite part of this build. I love how they came out.

Step 18: Moving It to the Front Yard Display

The pumpkin comes apart in 4 pieces. I moved it to the front yard with the help of one other person. The center section weighs a lot so we did have to take a break once. Once in the front yard, we set it on small pieces of 2x4s to keep it elevated just a little bit so hopefully moisture won't destroy it.

I then had to create the scene. The 12 foot Home Depot skeleton was moved as close as I could to be lifting the lid. The knee is actually touching the side of the pumpkin. His arms are wider than I thought so just one hand is touching the lid. I added a 5 foot skeleton climbing out with seeds and pumpkin goo. Other 5 foot skeletons are taking away pieces, or goo/seeds, or just laying down on the job. And the giant oversized skeleton from last year just finished carving the pumpkin with the 7 foot carving knife.

Step 19: Mistakes I Made and What I Would Different

Overcoming 1 foot flat edges of the blocks was difficult to do as I was shaping it to be curved. If I had to do it again, I think I would try to cut the blocks in half first making them 6 inches tall instead of 12. Then I would glue up 16 rings instead of 8. More work initially but less in the long run.

4 rings glued together weighs a lot and is hard to move. I think 3 rings max should have been the biggest piece. I didn't think it would be that bad but once the glue, sand, and paint was on, it weighed an awful lot. My shoulder is still upset with me when I lifted it solo to put it together for final touch up paint.

There are more expensive coating for hard coating foam. Sand and Glue work but are definitely not even close to the best and it is really messy to work with. I think spending the money on an actual hard coat might just be worth it. Fiberglass, spray on polyurea, or bedliner spray designed for foam are all options. And they would make the pumpkin last way longer but this was just a Halloween prop so I am ok with how the glue and sand method works.

Step 20: Halloween and Skeletons for St Jude

We are working with St Judes again this year with a group of haunters across the country to raise money for kids to get better and be able to come out and enjoy the displays in person. We have a goal of $100,000 in just 40 days but I think we are going to make it. If you scan the QR code in the photo, it should take you to the fundraiser if you want to see the progress on our goal.

I did actually find a pumpkin stack right at the end of September. So I made the top pumpkin and now I have the real thing. I think mine is more fun but I still like the pumpkin stack.

Our local police are awesome. They stopped by to say hi, let us know they are doing extra patrols, and to take a photo. They love what we are doing with St Judes and are happy to help any way they can.

I hope you enjoyed the build and my display. Happy Halloween All. And I have no idea where I am going to store it for all those wondering. If you have questions, ask in the comments and I will try to answer them all.