One of the things you may notice from all of my projects is probably my love for cardboard and lamps :)
My new creation mixes both these things, so working on it was really fun! I made some mistakes at first, and that made the work even longer, but they actually opened up my mind on new ideas that can be made with this technique.

This lamp is a dodecahedron composed by many pentagons that have been joined together. Composing it isn't as hard as it may seem, I must warn you though, that you'll need a lot of patience and time to cut all of these pieces by hand!
Don't worry, the result will reward you, believe me! ;)

The Featured Author Contest is what pushed me to make this cardboard lamp, and I've come to realize how much I missed creating lamps! Thank you for this opportunity Tarun Upadhyaya! :)

I'm finally selling this cardboard lamp in my Etsy shop! :D Check it out here!

Step 1: What You Need

Cardboard - I used a thin one because it was easier to cut by hand
cutter
ruler and pencil
hot glue
white glue
LED* light bulb and bulb holder

*the LED light bulb is very important because it won't burn the cardboard.

Step 2: Draw the Pentagons

Draw 11 regular pentagons on your cardboard. In case you don't know, a regular pentagon is a pentagon that has equal sides.
The sides of the pentagons I made are 6cm long (2.36 inches) but this is up to you anyway. The most important thing is that all the pentagons must be equal. Try to be as accurate as possible!

In case you don't remember how to draw a perfect pentagon (I didn't), take a look at this video.
I first drew it on a piece of cardstock, cut it, and drew its outline on the cardboard multiple times. Drawing them was much faster this way.

Step 3: Cut the Pieces

Now draw 5 smaller pentagons in each of your 11 pentagons. They need to have a distance of about 6 mm (0.23 inches) from each other, as you can see in the first photo.
All you have to do is measuring 6mm from the the sides and trace a line.
These smaller pentagons must be one smaller than the other.

When you are finally done drawing them, cut them very carefully using a cutter.
I decided to remove the central pentagon, but you can keep it if you like.

This is the longest step to make, but not very difficult! ;)

Step 4: Compose the Pentagons

Let's consider your first group of pentagons now:

lay the biggest one on a table and glue the next (smaller) one on it placing its angles on the sides of the big one. They'll create 5 small triangles all around.
It looks like a star, doesn't it? :)

Now glue the next pentagon on top, always turning it like you did before, so that the angles always match the previous pentagon's sides.

Keep adding the next ones following this pattern, one after the other.

You can either use white glue or hot glue for this. I used white glue, but it doesn't make a big difference.

When you are done with the first group of pentagons, proceed this way with the other 10 groups as well.

Step 5: Compose the Lampshade

Now that all of your pieces are done, you can compose the lampshade.

First of all lay a pentagon on a table (or something that keeps it flat).
Apply hot glue on 2 adjacent sides and glue a new pentagon on each of them, making sure to place them in a way that their 2 vertical sides also touch each other. You'll notice that in order for them to touch, they need to be lifted up a little.

Complete the first round gluing 3 new pentagons on the 3 left sides of the "base".
You'll obtain something that looks like a bowl.

Add a new piece on top of 2 of them, gluing 2 of its adjacent sides on 2 pentagons, as you can see in the third picture.
Do the same all around the "bowl" gluing the 4 pentagons you've left.
All the 5 pieces of the second round must touch each other too on their sides: to do this, you need to place them as if you were closing the "bowl" to create a ball.

Turn the "ball" upside down: your lampshade is done!

Step 6: Cut the Base Pieces

Draw about 8 new pentagons on cardboard, just like the ones you made in Step 2.
The number of pieces you need for the base depends on how thick your cardboard is and on how thick the base of your bulb holder is. For this reason, make sure to make some tries with it. You may need to remove or add some.

When you are sure of the number of pentagons you need, draw a smaller pentagon in each of them, at about 1cm (0.39 inches) from the border.
Cut everything using a cutter, removing the central part.
What you'll obtain is new equal pentagons.

Glue them one above the other with white glue (or hot glue), making sure to match their angles and sides together this time.

Step 7: Make One More Piece

This last piece is the one that will hold your bulb holder.

So, draw one more pentagon on cardboard, just like the previous ones, and draw the outline of your bulb holder in the middle.

Cut both the pentagon and the round outline you drew.
Remove the central piece so that the round hole is free for your bulb holder to be inserted.

Glue this new pentagon piece on top of the rest of the base, always matching sides and angles.

Finally, turn the base upside down and cut a thin section at the bottom of one side, so that the cable will pass through it and the lamp will be steady.

Step 8: Lampshade + Base = Lamp!

All you have to do now is inserting the bulb holder through the hole in the base, and finally place the lampshade you made on top of it!

If you want your lampshade to be perfectly firm on the base, glue some small pieces of cardboard on the base, very close to the sides, like I did here.

Light up your new lamp and enjoy the spectacular light effects it creates!