Heart Breaker Shirt - FAIL?

We had a craft FAIL, for some reason our Valentine's shirts did not turn out as we hoped.

When I saw the idea on Pinterest, and it seemed like a great idea and easy enough for the boys. An added bonus, was that I had all of the supplies on hand, so we gave it a try.

 We gathered the super simple supply list:

sandpaper, crayons, shirts, card board, scissors, pen, and foam letters

 I traced the foam letters, so that we would have the words "Heart Breaker."

The tutorial said to remember the image would be reversed...I did my R backwards and it had to be corrected.

I then cut everything out, and made a very simple heart shape.

 I set up a place for the kids to color the heart.

The texture of the sandpaper, was a strange surface to color.

 I colored the letters black, while the kids went to town coloring on their sandpaper hearts.

 I setup the colored hearts,  used parchment paper, and used the iron to melt the crayon image.

Not sure what happened, but the sand paper seemed to absorb the crayon.

 I wasn't happy with the out come...as the heart barely showed up.

*I love the concept of the project, but I cant pin point what what went wrong.

*See the inspiration here.