Calculating the shrinkage of shrink plastic

Here's a little quickie for you...  I'm in the middle of a project that uses shrink plastic and this is a neat trick I found for calculating the shrinkage of my shrink plastic. 

The brand that I'm currently using says that it shrinks to 20% of its original size, but I wanted an easier way of working out what size of shrink plastic I need to start with.  Not all brands shrink at the same rate and a 20% shrinkage is a comparison of area.  It does not mean that the length and width measurements shrink to 20% of their original size.

With a ruler, I drew a line close to the edge of my plastic and then marked on the line each cm up to 5cm. (As you can see, I did it twice to show the comparison of before and after.)

I then shrank one of my little 5cm rulers in the oven and the 5cm measurement shrank down to 2.05cm.

5 divided by 2.05 = 2.439

Therefore, if I know how big I want my final shrink plastic shape to be, I just need to multiply the length and width of my design by 2.439 to find out the size of shrink plastic I need to start with. OR, simply increase the measurements by 243.9%

This method is really useful when, like my current project, your final piece needs to be an exact size - or thereabout anyway.

Here's a sneak preview of one of the things coming up soon... 5 Brownie points for guessing what it might be!

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