Make your own 'Privacy Booth'
This is a picture of my desk in the afternoon. Not only is there a lot of stuff all over the back of it, there is harsh sunlight streaming in. I'm horrified to show you how mortifyingly messy it is (this is after I cleaned it), but I'm sacrificing my dignity to make a point. You can easily transform an almost un-workable space like this into a very conducive workspace by using a simple tool - and you can build this tool yourself out of cardboard.
Materials:
Piece of cardboard (~24" long)
Ruler
Pencil
Knife
Tape (optional)
1. Start with a piece of at least slightly stiff cardboard. It's best to choose something that is off-white, ideally neutral grey. You should be able to buy a piece of cardboard like this at an art store. You might have to buy a really big piece, but that's actually great because then you can make more than one (this comes in handy) or experiment with different sizes. The cardboard backing of pads of paper can also make excellent privacy booths.
This piece I have is 24"x18".
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2. Orient the cardboard so the longer side is horizontal. Divide the length into quarters and mark off the outer quarters. I marked off 6" from each side.
*Note that the side you are drawing on will be the back. Make sure to choose the nicer side to be the front.
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3. Gently score the cardboard along the lines you've drawn. Do this by holding your ruler firmly with your non-dominant hand against the line you've drawn. Run the knife along the ruler without pressing down into the cardboard. You might barely exert a bit of pressure with a finger on top of the knife.
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4. Bend the cardboard along the score lines. It should bend easily. If it doesn't, or it starts to crease instead of the outer layer breaking open, then you might need to score a bit deeper.
*If you're worried you scored too deep, you can reinforce the hinges with masking or drawing tape (don't use scotch tape). I suggest you fold the flaps in, then tape. This will ensure you can still bend it - if you tape it with the flaps laid out flat then it might be too tight to allow you to bend it. Also, make sure you tape on the outside so that you don't have tape stripes behind your drawing subject!
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5. You now have a privacy booth that will block out the mess on your desk and help you see shadows when you're drawing!