Mugs and plates update

On 8/30 we posted about buying dollar store plates and mugs and decorating with sharpie.  We were instructed to bake them for 10 minutes at 150 degrees.  When I took them out of the oven I ran a damp paper tower over the art work to make sure it didn't run and it was ok.  BUT when my Grandma washed her mug the other day, some of it started coming off.  After further research we wanted to update you to bake it for 30 minutes at 150-200 degrees to make sure that it doesn't come off.  If this is a decorative plate then no need to worry but if it's a dish that you are going to use frequently, please lengthen the time to bake to ensure you don't lose all your hard work.  Thanks!