Don't leave them in the sun

Never ever place your acrylics in the sun !!!

Clear acrylic balls can magnify sunlight, so you have to be sure not to leave them out in direct sunlight, or even sunlight coming through a window. If you are using a clear acrylic ball outdoors in the sun it may cause stinging of your hands, body or legs. Always make sure to store these balls away from the sun because they can act as magnifying glasses and easily start up fires!

A colored ball acrylic ball will not do this as much, depending on how dark the ball color is.

Somebody on Amazon told:

"My grandson left his acrylic on his mother's leather car seat, it burned a hole in it like one inch round, thru the leather! He knew not to leave it in the sun, but had forgotten. I wish I had purchased the bag for it ...Other than that the ball is beautiful and he handles really well . He is tall and has large hands. He is skinny , and I think the weight of the ball will strengthen his arms. Very happy with this purchase, my daughter is not."

And some more examples.... (not especially contactjuggling balls, but you get the picture...)

11 August 2009 - Fire started by crystal ball on windowsill destroys flat

22 March 2012 - Snow globe starts fire at Oregon home

15 October 2014 - Crystal becomes ball of fire

 Destroyed: The blaze caused over £10,000 of damage to her kitchen, living room and bathroom

At Firetoys they sell this bags, but offcourse you can find them too in other juggle stores. If you are a littlebit creative you can make one yourself.

O, and remember: The sun moves too !!!