Easy Treasure Chest From Cardboard Box

Would you like to make a nice looking treasure chest quickly and in easy steps? Here’s how I did it!

I needed a treasure chest for my daughter’s birthday treasure hunt (no pirate theme though, Nahrrr). I had an idea of what I wanted it to look like and the materials I was going to use, so I had a plan but made no drawings for this project, so I haven’t got any, but I did take photos for documentation and wrote this instructable. I may make drawings later on.

Once I chose my approach it was really just going at it and spend time on it whenever I had the time i.e. mostly every other evening or so. I finished it in about a week and a half. With this instructable and some preparations you could do it faster than that.

Many chests are made some hard wood and iron, but I don’t have any lying around, much less a real handy and lightweight chest. To build it fast and cheap I chose a corrugated cardboard box that I did have lying around. That would be strong enough for the candy bags and I saved time building the box itself.

For this project I used:

Metric units: 1 cm = 10 mm ( 1’ = 2,54 cm)

Materials:

Cardboard box dimensions: (Note: with this building method the exact size isn’t important)

Height: 11.5 cm (‘ish)

Width 15.5 cm

Length 21.5 cm

3 mm corrugated cardboard cut from a slightly bigger box

1 mm corrugated cardboard cut from another box or something

Some length of rope that I bought cheap at a hobby store

A small amount of general office tape

Tools:

Glue gun and glue sticks

Exacto knife/hobby knife with harp blades

Aluminum ruler with steel edge for cutting (anything that allows straight cuts, measurements, and bending the cardboard with would do)

Cutting mat to avoid cutting the table

Flat black spray paint (cheapest one available)

Gold and silver pens for coloring (use whatever you want; paint, crayons, colored tape, etc.)

Open the box and place it on a flat working surface. You want to have a nice even edge so measure from the surface and mark where to cut. Don’t make the cuts exactly along the bends that make the lids but slightly lower than that where the cardboard is intact. You want an even height all the way around, as your own lid will fit onto this. Make the cuts carefully with a steel edged ruler or something similar to guide your knife.

Note: Aluminum and plastic rulers are in my experience not suited for cutting guides as the blade easily cuts into them, but you can use anything that allows an even cut. I sometimes use pencils or wooden blocks (when I’ve misplaced my trusted ruler) because the contact point with the knife blade will be raised above the material to be cut and is therefore less likely to be cut into. This raised contact must be countered with careful control and most of my cuts made this way are not straight lines.

My box ended up being 11.5 cm measured from the table but it is more important with an even cut, so if you have to, you make adjustments. If you end up with an uneven height all the way around then either make new cuts or read Step 3 for a solution.

Another note: In my project I wanted to keep one lid so I didn’t have to invent a hinge but this gave me a bit of trouble later on which was solved in Step 4.

I decided to simulate iron edges with raised cardboard which would look good. I left the bottom free as my box was very stable by itself. The “iron” edges would be 10 mm wide all around and 3mm thick which seemed about right for my box size. The width should fit the look on some real chests so feel free to choose a width that fits your version.

Note: it looks good when all edges are equal in size. Also you could use non-corrugated cardboard for the “iron” edges or even just paint the edges… Your choice :-D

Mark and cut some sections for the horizontal edges: 4 long and 4 short edges on the basic box itself and 2 long edges on the chest lid. Make them a bit longer than needed so you can fit them later. The ends of the lid were made from single pieces, so I didn’t count the short ones for the lid.

Careful measurement, marking and cutting should yield a nice even width on all pieces and don’t forget to cut across the corrugations to avoid collapsing strips (and it looks good).

For the vertical edges I decided to fold the cardboard around the edges and therefore needed wider strips as I didn’t want the corrugations to be visible on the ridge itself. Now apply a minimum amount of math to the project: Add the two sides with half the thickness of the cardboard to allow for bending without losing the width of the edge: 10+10+1.5 = 21.5 cm (width + width + half thickness of cardboard). Again cut them longer than needed to allow for fitting.

Mark the centerline of the wider strips and press something with a hard edge down the middle of it. A ruler is fine for this, but anything with a straight edge should do such as a wooden chess box. This compresses the cardboard corrugations and makes it easy to fold along the compressed lines.

Note: Some of my compressions were slightly off and had to be adjusted by pressing the right places to get it right. If I needed to make further adjustments or had made the folds non-parallel I would have to make new ones.

Now on to the first assembly:

Begin with the vertical “iron” edges. Apply hot glue to the inside of the bent pieces (one at a time) and press them in place along to the box’s edges while making sure that you place each one onto the flat surface, where your box is. This will help stabilizing the box. The pieces should stick up above the box’s edges which is good. Now cut them down so they are flush with the top edge using a sharp knife which you are naturally cautious with.

Proceed with the horizontal pieces. Dry fit one piece at a time against the vertical “iron” edge and either the top edge or the flat surface. Mark the exact place to cut the piece and make the cut in a safe manner.

Apply hot glue to the piece and put it exactly where it was dry fitted. Then proceed with the next one and repeat until you have all edges covered on the box itself.

Note: In case of flaws on the top edge from Step 1 that you want to hide you might want to cut the vertical strips longer than the height of the box. Just make sure they are exactly the same length at around 1-2 mm above the top edge. This will give you the new height. When hot gluing the top strips into place for this new edge it would be a good idea to flip the box over on the top and use the work surface to guide the exact placement.

The main purpose for the hinges is to keep the lid in place and therefore need to cope with a lot of wear, so they need to have some strength and a solid contact with both the box and the lid, which can be achieved through many means. Small brass hinges can be bought but I chose to stick with cardboard and hot glue. The cardboard itself will tear quickly and will need some tape or other material (such as band aid perhaps?) to reinforce the bends.

If you did like me and cut only three parts of the original lid off, then you will probably realize like I did that you cannot use the lid as a hinge… the bend will make the lid push against the newly installed top edge and either prevent opening or you would have to accept a gap. If you’ve done like me so far, then do like me once again and cut that last part of the lid off trying to achieve that even edge…

The 3 mm corrugated cardboard could possibly be used, but the bends/hinges seem to be too large. Non-corrugated cardboard doesn’t handle repeated folding very well in my experience. This is where the 1 mm corrugated cardboard comes in handy. It’s not too thick and handles bends nicely as long as it is reinforced.

Cut a couple of wide strips (mine were 3 cm) and significantly longer than needed as you can see in the photo. This makes them easy to manipulate into place and allows for fitting unto the lid later.

Mark at least 10 mm + half the thickness from the end of the strips and then add 3 mm and mark that on the other side of the strips (the 3 mm is the thickness of the “iron” edges). Make sure that both strips are equal. The first mark will be on the outside and the next on the inside, so make the first bend on the outside (at 10.5 mm) flip the strips and make the next set of bends on the inside (at 13,5 mm).

Dry fit them to find a spot that looks good. Mine were placed 8 cm apart and 3 cm from either inner edge of the “iron” edges. While dry fitting mark where the hinges will bend and make the bends from the outside. Apply your chosen reinforcement on the inside of the hinges so they’ll be invisible. THEN you glue them into place with hot glue…

Note: Time will tell if I got the reinforcement right.

Up until now things have been pretty much straightforward except for the hinges perhaps, but this is the lid which is perhaps the most prominent feature so we want his to look good and fit perfectly onto the box/chest. Dry fit to make sure you are on track as you go along.

Measure the width of the top of the box on the outside but on the inside of the “iron” edges. At this point this should be easy to see from above. It could be measured before any “iron” edges are applied, but the hot glue and “iron” edges could warp the cardboard box a little bit, so now is fine (besides I forgot to measure beforehand).

Make half a circle on a 1 mm cardboard piece for each end using the measurements. Mark them to be sure which end is which. Cut both pieces out and that’s basically the shape of the lid… Come to think about it I chose the 1 mm because I ran out of pieces of 3 mm. You can easily use the 3 mm board here just like it is on the box.

Aaand it’s time for math again. I decided to make the lid simulate 7 “planks”, but you can make as many as you want. 1 “plank” will give you a flat top, 2 will become a triangular shape, and 3 will give you a resemblance of a curve. Therefore I suggest at least 3 but it depends on what looks right on your version (You could even bend it in so many places that there won’t be any “planks” visible). Calculate the circumference on one of the half circles:

Circumference = 2*π*radius or Circumference = π*diameter

Divide by 2 to get the circumference on the half circle.

In my case the diameter was 14 cm which gave the half circle a circumference of 22.1 cm (rounded off). This would give the 7 “planks” a width of slightly above 3 cm. I chose 3 cm wide “planks” and divided the remaining 1.1 cm into two thin “planks” that would be vertical. In essence this would actually mean that there would be 9 “planks”, but 2 would be hidden. The bent corrugated cardboard is 22.1 cm long and as wide as the inside of the box. Of course your calculations would yield a different result, so choose a width of the “planks” that allows for the 2 minor vertical “planks”. It doesn’t even have to be an even number.

Note: You can see on my lid how I had to use part of a lid along with one side to get a piece big enough. The creases would have to be covered.

Once you have cut out the plate as perpendicular as possible you make the marks for the “planks” and press a ruler down to make the bends as before. Make sure that the marks are centered so both end sections have the same width. When you have an uneven number of “planks” you want to make the middle one parallel with the bottom edge in the middle of the half circle. If you decided on an even number of “planks” the middle bend will have to be above the center of the chest at the apex of the half circle.

Place one of the half circle ends on your flat surface and put the bended “planks” vertically on top of that and make the outside bends of the middle “plank” touch the outside of the half circle parallel to the edge in the middle of the half circle. Apply hot glue to the topmost part on the inside only and let it set while holding it in place. Once set you simply make the next bend touch the half circle and hot glue on the inside and go on until you reach the bottom edge. Do the same for the other side. Don’t hot glue on the outside as this will be covered by the “iron” edge.

Now flip it over and place the other half circle on your flat surface. The “planks” are now hot glued on the inside to the end plate just like the other end. Check that the lid structure fits your box top and make adjustments if necessary. Cut away the material that exceeds the “planks” and you have your lid base structure complete.

For my treasure chest I decided to make the end edges in 1 piece that would fold around and be hot glued to the outer side of the “planks”. Next time I may want to make a wide strip just like the vertical pieces and hot glue them to the “planks” first and fold them onto the ends afterwards.

After having cut the excess material off the ends of the lid, place it vertically on top of a 3 mm corrugated cardboard piece that is larger than the profile of the lid. Draw a line as close as possible to the shape of the lid including the bottom edge. For every straight line make a parallel line on the inside towards the center. This should be the same width as your other “iron” edges and will form the inner edge of the “iron”. Likewise make the corresponding lines on the outside of the contour but remember to add the half thickness. In my case it was 10 + 10 + 1.5 = 21.5 mm outside of the inner edge.

Cut out the center section inside the inner line free and cut away the material outside of the lines. Hot glue this part to the lid so it fits the contour. The bottom edge must still fit the end plate and the box. Once set make a V-cut from the “plank” edges outward perpendicular to both on either side. I attempted to make a cut, that would allow the bended flaps to align perfectly, but made the tip of the triangle too wide. This gave a slit between the flaps when folded and I had to continue like this to get it look the same all over. That actually worked out well in the end but you can make the triangle cut with a fine tip and reduce the slit. When removing the triangular pieces twist those inwards over the lid, so that any tear will be covered by the bend and glue.

All flaps must be bent and to do that I used a metal plate that I had handy. You can use the end of your ruler or anything that helps you make a bend on only one flap at a time. When you have finished then apply hot glue to one flap at a time and hold it in place until set. Then do the next one etc. When finished with this end of the lid repeat the process for the other end.

For the edges along the horizontal lower edge you take the strips that you prepared earlier in Step 2 and hot glue them into place. To make the lid fit the box well apply the strips while the lid is on the box and use this as a guide. Be careful and you will have a nice fit. I wasn’t and had to carefully rip the strips of and reapply them…

If you were fortunate enough to avoid the crease that I had, you can proceed with the next step. Otherwise (or if you just like the look of the extra strip) then follow me on the last bit of this step. Cut another strip as wide as in Step 2 and make it longer than you need. Hot glue this strip to the center of the lid so that it covers the crease. Only hot glue the strip to one “plank” at a time. This ensures bends that fit very well. Once you reach the last “plank” you simply mark and cut excess material off and hot glue the last bit in place and your lid is done.

Those hinges need to be hot glued to the lid and you do that the same way that they were glued to the box. The difference is that you fit the bends to the contour of the “iron” edge of the lid rather than measure from the other end. Mark the first bend including the half thickness and then mark the next 3 mm further from that to accommodate the thickness of the “iron” edge. One hinge is easy to make but it can be tricky to align both so that they work in unison. It isn’t impossible though. Go ahead and bend them with regard to which direction the bends need to be. The first should be on the inside and the next on the outside. Again apply hot glue to one hinge at a time and press it onto the lid.

There you have you very own cardboard treasure chest (without a lock or handles).

Note: I didn’t have time to create or apply a lock. I could have made a fake one, but decided against it. I wanted it to actually work and kept the option of adding it later. For this reason I don’t have any suggestions on the subject but feel free to explore this at your discretion.

This step is entirely up to you. If you like the look of your cardboard treasure chest just skip to the last step.

I bought a cheap flat black spray can (the cheapest one I could find…) and sprayed the treasure chest on all surfaces except the bottom and the inside. When spraying paint remember to apply a thin layer and follow the spray can instructions. On my can it stated I could apply the next layer within a few minutes so I did. As soon as the paint appears dry you can apply the next layer. Try to angle the spray so that you get paint into the corrugations on all of your “iron” edges and be patient doing so. Rushing this can result in the paint running.

Note: Thin layers are good layers! Thick layers make the paint run and probably warp the cardboard.

If you want to you can go ahead and spray paint the inside as well. I decided not to do so as I wanted the treasure chest to contain candy. Maybe one day I will upgrade the inside with some velvet cloth… red perhaps…? I bet that will look good!

The paint scheme you choose to apply over the flat black paint is up to you (even the flat black could be swapped for any other color to suit your needs). Just have fun doing it where there is a lot of fresh air. Here are a few examples:

- Paint the “planks” and sides with brown to mimic real wood with tree ores in darker tones or even black

- Do the same with any color (base color and tree ores in darker tones) and have a colorful chest

- Paint the “iron” edges a metal color like aluminum or silver. Apply a little brown, red, or black paint over this and smear it out if it’s too bright or choose a darker metal color

- Paint the “iron” edges in lighter or darker tones of your treasure chest or even in contrasting colors

- Apply paint here and there and smear it over the surface

My wife chose the colors for the cardboard treasure chest and painted it. It looks awesome!

Details can really add character to your new treasure chest and a few modifications could be necessary to strengthen the stability because… those hinges aren’t perfect…

Weathering can make your new chest look old and used. Rivets can be added by gluing suitable shapes made from wood, plastic, modeling putty or just use real rivet or nail heads. What you do is entirely up to you.

First of these details I wanted to have some sort of handles to carry the treasure chest. I considered using iron rings, bet came across the rope that you see in the pictures. It was cheap and fit the bill nicely. I marked where I wanted the rope to go through the cardboard and then carefully pressed a screwdriver or a pen inwards, so any tear would appear on the inside. Then I put the pieces of rope through the holes and applied hot glue to be sure that the tear wouldn’t split the cardboard and ruin the chest. I considered some options of fastening it securely but realized that the easiest way was to simply hot glue the rope to the inner surface a little at a time by in a circular fashion. This would be relatively flat and strong enough to handle some weight.

Second, the hinges started to come apart rather quickly and I had to apply more hot glue to keep them in place. I cut off the excess glue with a knife and the hinges haven’t split again… yet. I did consider using threads to sew the hinges into place, but didn’t want to. I also considered using some sort of pins to hold them in place but couldn’t see how to do that with a time limit coming up.

Third, the lid felt a bit loose, so something was needed to ensure correct closing. If it is loose, then something will wear out and that’s most likely the hinges. On real chests the hinges are quite strong and don’t need any guides, but this is rather weak cardboard hinges… I decided to add some guides to the two corners furthest away. I chose a design with sloped edges on two sides to guide both the front and the sides to the correct position.

I cut two rectangles from cardboard leftovers and made a bend on both down the middle. Then I cut a triangle shape around 15 mm from an edge from the bend towards the same edge on both sides of the centerline. You can make these equal in width, but I cut one side slightly wider. I did it to both rectangles, so they were nearly identical. I pressed the pieces perpendicular to the first bend exactly where the triangles began and then I bent them opposite directions of each other to mirror their shapes. I applied hot glue and let them set.

Then I dry fitted them and cut them down so they would fit nicely in the inner corner of the lid and hot glued them into place. I call them teeth…