Introduction: Cardboard Lumber
How would you like an incredibly strong, cool, and cheap building material for making lightweight tables, chairs, shelves, or anything else you can think of. Reusing cardboard to make furniture has always been a good idea, but the results I've seem have been either incredibly complex, or shoddy looking.
By laminating sheets of cardboard together into a large block and cutting this up with a table, or circular saw, you can create cardboard lumber of any dimensions you want: 2x4s, 2x8s, 4x4s. If you alternate the grain of the corrugations you can create plywood. If you glue your lumber together end-to-end you can create strong honeycomb-like boards.
You will only need three things to create cardboard lumber:
1) A Saw
2) Lots of cardboard
3) Glue... lots of glue
Step 1: Types of Saws
Table Saw: The best saw you could possibly use to do this is a table saw. You can adjust a table saw's fence to help you cut perfectly uniform lumber out of your cardboard block. This allows you to easily mass-produce cardboard lumber. Because of a table saws fence, you should be able to cut lumber twice as thick as the max height of your blade by cutting once, and then flipping your cardboard block over and cutting through entirely.
Circular Saw: If you're really good at cutting straight lines and have no other option then I guess you could give it a try.
Hand Saw: Possible, but too labor intensive for me.
Band Saw: If your band saw is as powerful as a circular saw than go for it, this could open interesting options.
Chain Saw: Messy...
No Saw: Unfortunately for people without access to saws, this instructable is not for you. I know it looks cool and all, but it's just not gonna work out.
Step 2: How to Get Cardboard
Super Moral and Totally legal free cardboard:
Save up cardboard from boxes your family uses. You'll be surprised how fast it adds up.
Go around town and ask any businesses if they have any cardboard you could take. It will likely be already broken down for you.
Super moral and Mostly legal free cardboard:
If you're in a hurry, or just lazy, you can drive around the back of stores and look through their recycling dumpsters for cardboard. Be warned though that dumpster diving is a crime, but most people will be fine with you hauling away some of their trash.
Maybe legal and moral free plastic cardboard:
Those corrugated plastic advertising and campaign signs scattered around your neighborhood are considered litter/unclaimed property in *some* areas. Snatch a bunch of them up fast and you'll have an awesome start to rock solid, corrugated plastic lumber (Be sure to use glue designed for plastic though. Wheatpaste won't work.)
Most of my cardboard came from my school cafeteria and my family's recycle.
Step 3: Prepare the Cardboard
I will be making a large solid block of cardboard with all the corrugations pointed the same way. If you want to make classic plywood, alternate the corrugations throughout the block. The second way could be stronger, but I'm going to make it this way because it looks nicer.
You have to cut your cardboard so that each single layer lays flat, and is completely filled with cardboard. The look and strength of your lumber will all depend on how well you cut your cardboard layers up. It would be best to have all cardboard meet at hard, squared off corners.
To prepare your raw cardboard boxes, you have to cut all of them into flat rectangles, removing all tape and anything you can to make them just cardboard rectangles.
Step 4: Stack the Cardboard
Before you glue everything together, stack the cardboard in a neat pile. It's okay if there's a couple little gaps, we're just making sure we have enough. I wanted to make a 4'x4' square of cardboard the thickness of how deep my saw could cut.
Now is a good time to estimate the sq. ft. of cardboard and see how much you can build.
Step 5: Get Some Glue
You have a couple options here, and by a couple I mean exactly two:
Wheatpaste: At less than a buck a gallon, this is what I will be using. You can view my wheatpaste instructable here, or basically heat 1:4 part flour/water until it get's thick. Wheatpaste, when made properly and applied correctly will be pretty much as strong as the glue that holds the corrugations of the cardboard together (they use a starch glue, white flour is starch...). It's used by paper machers and also graffiti artists to post paper pictures to concrete walls and create a rock hard irremovable poster. I would recommend adding any bacteria deterrents you have (see instructable).
1:1 Wood Glue: You might be able to find a gallon of wood glue at your local hardware store for about $10 if you're lucky. This should be diluted with water 1:1 because we're covering such a large area, and only want a thin coat, and also to help the glue soak into the cardboard. This comes out to $5 per gallon. The advantages of this is it's much stronger, the corrugations will always rip before the wood glue seams, and is easier to make and apply (but not much). After doing this with wheatpaste, I would recommend this way, simply because the wheatpaste is not as sticky as it needs to be.
Note: You could also use Wallpaper paste I guess; it comes in a powder at the hardware store.
You will need a minimum 2 gallons of either to properly glue the amount of cardboard I am doing.
Step 6: Glue!
Lay our your cardboard on a flat surface and get your first layer ready. Apply a VERY large amount of glue to one section by POURING it on the surface and spreading it evenly. If you think you used too much, then you almost have enough glue on. Now apply glue to the piece to be put on for the second layer. Don't think of this as glueing cardboard together! Think of it as paper mache WITH cardboard! Lots of glue! Continue fitting cardboard together neatly and gluing it until you reached your last layer and you're out of cardboard.
My 4x8ish block was a little thin, so I cut it down the middle and doubled it up.
Step 7: Wait...
Clamp down your pile, or stack a bunch of things on top. I would wait at least a couple hours in the sun. Overnight if it's indoors.
Step 8: Cut!
I used a circular saw and a T-square to cut three even sides. I was pretty surprised with the firecracker-like sounds the cardboard made when i cut it.
Then I used a table saw to cut everything into 1.5" strips. I would highly recommend a partner to help you cut up the block. It's heavy and unwieldy.
Step 9: Honeycomb Plywood
Once you have your lumber, you can either use these individual pieces, or you can glue them, edge-to-edge and create a very, very strong block of cardboard suitable as a tabletop or seat. Because the corrugations are all vertical (as a tabletop) and not horizontal, it has much greater strength.
Step 10: Build!!!
Use your imagination! This is an entire new building material that you have to figure out how to use.
To further strengthen your projects, you can seal the whole thing in wheatpaste like i did in the previous step.
Ideas for using this stuff, suggest anything you want to add:
Scapile (my original inspiration for all of this)
A cardboard playhouse made by Piersg
a MASSIVE amount of completed woodwork projects (search with the "view more tags" link)
lots of lumber plan blueprints
Andy Lee coffee table
nice table design
cool sitting bench
snap together table from instructables
Please rate and comment...
Can we stop talking about the environment guys? I wasen't really trying to make any point that this would help the environment anywhere in my instructable. If you have easy access to cardboard, flour and power tools, then you might be interested in making this. Go ahead, try it and tell us what happened. If you don't like this idea, then please suggest better alternatives. Please calm down the comments on your assumptions about how cardboard and wheatpaste effect the environment.