Introduction: Build a Play Stove From Recycled Laminated Cardboard

This Instructable covers how to turn old cardboard boxes into strong, rigid cardboard panels that can be used to make a safe, simple play stove. The best part about the play stove is the oven; you can store a lot of play food in a play oven.

Since the most salient feature of a new toy is generally its novelty, you can make a perfectly adequate play stove by flipping over a cardboard box and drawing some burners on it.  This stove is insanely overbuilt; I was mostly looking for an excuse to try out making "plywood" out of cardboard.

So, on to the cardboard laminate. A useful fact from the world of mechanics of solids is that the flexural rigidity of a plate increases with the cube of the thickness. In layman's terms this means that if you double the thickness, you make it eight times stronger. Corrugated cardboard already takes advantage of this fact by weaving a sheet of kraft paper back and forth between two flat sheets of kraft paper, making it much stiffer than it would be if the layers were all flat.

By gluing up many pieces of corrugated cardboard, we can make cardboard panels that are an inch or more thick and as large as we want. At 1" thickness, these panels are already quite strong; they can support several hundred pounds across a 24" span.

Not only are the panels made from recycled materials, they are themselves recyclable, so when all the fun has been exhausted, the stove can go out with the rest of the cardboard recycling.

Step 1: Save Your Cardboard Boxes

This project got started when we had a superabundance of cardboard boxes following the installation of a new bathroom sink. While it isn't strictly necessary to use big pieces of cardboard, it makes assembly easier and the resulting panels look better. So this is a good project to undertake after you take delivery of some large, life-style changing object such as a new refrigerator or dryer.

Once you have some "big" pieces, let the usual assortment of smaller shipping boxes accumulate until you have a good supply of raw materials, or your spouse starts yelling at you. Break down the boxes and remove any staples or overlapping segments---it's important that all of the pieces in a given layer be the same thickness. If you have boxes of varying thicknesses, sort your boxes by thickness.

The other things you'll need are:
* a gallon container of Elmer's glue
* a plastic drop cloth
* a utility knife
* some kind of saw. (I used a table saw, but a hand saw would work fine and would probably be less scary.)
* kraft paper packing tape

For the play stove, you also will need:
* 4' of bungee /shock cord
* some stove knobs, handles, black paper for the burners etc.

Step 2: Lay Boxes Out on Plastic

Put the plastic dropcloth on the floor to avoid making a huge mess.

Look over your cardboard riches. Pull out the very best (large, flat, rectangular) sheets. Half of these will go on the top of the laminate and half on the bottom. If you can make the entire top and bottom layers from a single piece of cardboard, that's the best; if not, try to minimize the gaps. This is for both structural and aesthetic reasons. Most of the strength of the panel is in the outer layer, and anywhere you have gap it will be weaker.  A refrigerator box cut into two big pieces, one for the top and one for the bottom, is ideal.

Anyway, set out the first half of your top-quality cardboard, with the "good" (unprinted) side face down.

Step 3: Glue Up Layers

Spread a thin layer of glue on the cardboard in preparation for gluing up the layers. Too much glue is your enemy here, because it's very difficult for water to get out of the laminate and glue blobs take forever to dry.

Here my little helper (age 3 at the time) is spreading glue with a plastic spackling knife.

Step 4: Keep Adding Layers

The quality of the cardboard in the middle of the stack has little influence on the overall strength; it's basically there to keep the top and bottom surfaces of the plate away from each other. You can use really low-quality cardboard boxes in the middle, including those annoying yet omnipresent boxes.

Just remember to avoid filling the gaps between pieces with glue.

Step 5: Cover With More Plastic Wrap, Weight, and Let Dry

After you've built up the cardboard laminate to the desired thickness, take the other half of the "good" cardboard and add it to the stack, with the good (unprinted) side up. Again, this layer actually matters, so try to do a good job fitting the pieces together.

Cover with plastic wrap and put some weight on the whole stack. I think we used boxes of books and magazines that we'd never finished unpacking from our last move.

Step 6: The Big Panel

After a couple of days the panel seemed to be dry. I decided to cut it up into useable pieces on my table saw. I was able to cut 8 16" x 24" panels out of the big panel below.

Using the table saw was a mistake; while you get nice straight cuts that way, the starting panel was so large that it was difficult to work with and therefore dangerous. Due to my excessive use of glue, there were also pockets of liquid glue in the interior of the panel to surprise the unwary and gum up the table saw blade. I haven't tried this, but I think a regular hand saw would work fine (it's only cardboard, after all) and would be a lot safer.

Step 7: Saw Up Into Panels

I ended up with seven 24" x 16" panels. Some of them were still oozing glue after cutting, so I set them aside for a "little while" that ended up being nearly a year. (Parents will understand.)

Step 8: Let's Build a Stove

Christmas was coming and Santa was already planning to deliver a pink play sink she had acquired on Craigslist, so I decided it was time to dig out the cardboard panels and build some more appliances. The little helper, now 4, was enlisted to help with the fabrication using some ridiculous story.

Actual assembly was done with a hot glue gun and about 22 yards of 3" kraft paper packing tape from McMaster-Carr. This stuff is awesome; it's cheap, it's strong, it recycles better than plastic tapes. I recommend it for all of your packing tape needs.

Step 9: Customer Focus Group

It's important to do pre-production testing.

Step 10: Set the Oven Floor

In this design, the oven floor is 11" off the ground, mostly for the convenience of the grown-ups. I had a large piece of double-thickness cardboard that fit perfectly into the space made by the four base pieces, and I was able to use a corner of the original cardboard box as a hinge for the oven door.

I didn't do the hinge quite right. Since my panels were an inch thick, I should have set the hinge so that there was at least a full inch of space between the inside surface of the hinge cardboard and the rest of the stove. I made the gap too small and had to remove a bunch of material from the door panel.

In order to make the front of the door look smooth I glued another piece of "good" cardboard to the front so everything was flush. With good planning you could use a single piece of cardboard for the whole front of the door, which would look best.

Step 11: Tape, Tape, Tape, TAPE

The edges of the cardboard panels are ugly, because all of the corrugations are exposed. You can cover the edges (and all kinds of other goofs) with kraft paper tape. It really doesn't take that long, and the little helper loved wetting the glue with a rag. (Watch out for paper cuts!)

Step 12: Structural Complete

The stove is pretty much together now. See the last page for dimensional drawings.

Step 13:

I bought some real stove knobs, also from McMaster-Carr. (At $2.45/ea, these were the most expensive part of the project.) To hide the bolts I countersunk them from the back, then put a piece of kraft paper tape over the holes.

You really can treat the laminated cardboard like a building material and saw it, drill it etc.

Step 14: Structurally Complete!

The stove is now finished, although the door falls open because it doesn't have any springs to hold it up.

We ended up wrapping the entire stove in kraft paper tape because it looked better that way. While I kind of dig the utilitarian look, I think play value for my kids probably would have been enhanced if I'd gotten some bright-colored contact paper from the variety store and covered it in that instead.

You can hide a lot of goofs this way.

Step 15: Door Springs

It took me quite a while (like, another two years) to get a good door spring design. I wanted something that closed automatically (vs latched) and that did not pose any risk of catching fingers, since now I had two little helpers in the family. 

My first try was velcro, which worked poorly; the velcro-velcro bond was stronger than the velcro-kraft paper bond, so they'd just rip right off. Plus the kids never put the door back up when they were done playing, because they're kids.

Finally I came up with the bungee cord strategy below. This works great; the restoring force increases as the oven is pulled down, but is near-zero when door closes. The cords are held by drilling two closely-spaced holes, threading the shock cord through and tying it on the inside. Simple, safe and reliable.

Step 16: Bling It Up

Since it's made of cardboard anyway, your little helper can decorate the stove to their heart's content.

Little helper is now not-so-little, being 6 years old and 4' 3". Her younger sister is 2. While the play kitchen has never been their favorite toy, the kids do still like it. (At least the pink commercial one isn't any more popular than the home-made one.) Popularity rises when friends come over, as cooking is a good group activity even when it is pretend.

Probably the best feature from my point of view is the large capacity of the oven. It can hold a lot of toys; this means the overlords can sweep in, pick up all the play food etc, and toss it all in the oven.

Step 17: Technical Drawing

Below is a drawing I made today of the final stove. It's been a couple of years since I put it together, so think this through before you start sawing as I might have messed up the dimensions.

The construction is basically:

* Cut out pieces. I started with 7 16" x 24" panels, but some of them weren't that great and being able to cut away parts of them was a bonus. The scrap just goes out with next week's cardboard recycling.

- 2 16"x24"x1" panels ("A"),
- 2 16"x21"x1" panels ("B")
- 3 11"x24"x1"  panels ("C")
- 1 18" x 22" x 1/8" (plus tabs and hinge) oven floor panel. 

* glue and tape 2 C's (bottom back, bottom front) and 2 B's (sides) to make a 4-walled structure.
* set the oven floor across that box. Do a better job with the hinge than I did.
* glue and tape 2 As (top back, stovetop).
* attach the final C to the hinge.
* bungee cord it.
* add the bells and whistles.

As mentioned I haven't tried standing on the play stove, but I've sat on it. It can certainly hold a couple of hundred pounds. I will be interested to see what other things people can make with laminated cardboard!