Wednesday, February 16, 2011
As you may know, we're loving tangram puzzles at the moment.
I had the idea today that I'd like to make some out of shrink-film.
I didn't know if they would turn out alright, as this involves shrinking plastic, and I didn't know how plumb (flush) they would be. They're not absolutely perfect, but I think the fit is true enough to be quite satisfying.
Here's how we did it...
We only used shrink-film (four sheets for two sets of tans), sandpaper, and sharpies - you can also use colored pencils.
For tools, we used scissors, cardboard, and two pieces of wood.
First you need to sand one side of the plastic both ways - horizontally and vertically so that your medium can stick to the film. Leave the other side shiny.
Our sheets are 8x11 inches, so I measured to make an 8" square. (From this, the final size after shrinking was about 4 1/2 inches square.)
I then cut it out, and used that as a template for the second square.
Note: if you haven't cut shrink-film before, do so carefully - it can tear pretty easily.
I drew a line across one of the squares, dividing it into halves -
these are the large triangles.
The second square I cut into halves by way of making two rectangles (each 4x8 inches).
One of the halves can be made into two squares - leaving the second square for the second set of tans.
The other half of the square - the large rectangle, can be divided up easily into two small triangles and the parallelogram.
Mark the half way point of the long side of the rectangle - in this case, at 4 inches.
Draw a line from this half-way point to the corner of the rectangle, making the first small triangle, and then cut it out.
Take this triangle, and using it as a template, draw another line, making the parallelogram and second small triangle.
You now have six of your seven tangram pieces - plus an extra square.
With the third sheet of shrink-film make another 8" square.
Cut this one also into two large triangles.
Cut one of the triangles in half - making two medium-sized triangles. One of these is the last tan, and the other is the medium triangle for the second set.
With the other half, you can make the two small triangles and the parallelogram.
Either use a small triangle from your completed set to make your first small triangle at the top of your large triangle,
or by marking the 1/2 point on both short sides of the triangle,
the cutting it out.
Use this as a template for the second triangle, leaving you with a parallelogram.
Now you have one full set of tans, and the square, medium triangle, the parallelogram and two small triangles for the second set.
With the last sheet, cut it square, and then just cut it in half, leaving you with the two large triangles.
Your two sets are complete!
Decorate them as you wish, using permanent markers or colored pencils.
Place them on a piece of cardboard, place another piece of cardboard over the top of them,
and put them in the over on 300-350 degrees (f),
After a couple of minutes, check on them,
and when they're finished (it really only takes like three to five minutes) take them out of the oven and carefully (they'll be hot!) put them on a cutting board and then quickly cover that cutting board with another wooden board so that they'll harden as flat as possible. (Press on it if it isn't very heavy.)
Aren't they beautiful?
Note: This was a true lesson in geometry for me, and I think it would be a great challenge for older children to try to figure out for themselves - ie to team up with another and work it out with paper to make the tans the most efficient way. It took some figuring before I could make two full sets with only four sheets - the first ones took me just a little over four sheets. :)