Heater fan making colors change/blotchy

I have not had this happen with my dehydrator, but be sure your icing is pushed as thick as possible for the task at hand. The looser the icing is, the longer it takes to dry (no matter what) and the more likely it can discolor/mottle. 

This is a problem that can happen if the cookie gets too hot. I know others that have experienced this using heater fans. I have had it happen using a heat gun as well as a dehydrator without an adjustable temperature setting.

I dry all my cookies with a dehydrator set at 100 degrees. I would try moving your cookies further from the fan or letting them air dry. Using a regular, non-heated, fan can also speed drying time and increase shine without having to worry about butter bled. 

I also dry at temperatures between 95 and 105 F. Have only had mottling issues (possibly) related to temperature when drying in my oven, which would only regulate as low as 150 F. Still believe icing thickness has a ton to do with integrity of color (color fastness). 

Thank you Julia for answering me. I haven't invested in a dehydrator yet and I have had no trouble since I put the heater farther away as well as also only using the fan at the beginning until i see a crust form. Also I am sorry i didn't see you had replied earlier. Since I am new to this site, I didn't know anyone had responded. Is there a way to get a message in my email that someone has responded to something you have posted?

Thank you so much for this Cookie site it is a true blessing.

Glad you're enjoying the site! Yes, if you click on "Follow this Topic" in the upper right of any forum post, you should receive email notifications whenever anyone responds to the post. But you must make sure that your email notifications are also set to allow forum notifications to be received. You can set all of your notifications (about forum posts, blog posts, clips added, etc.) by selecting "Edit Profile" in the upper right of the site and then "Your Notifications". More about setting email notifications can be found in this post: http://cookieconnection.juliau...-email-notifications 

I have had this happen a few times- both in my dehydrator or if I have set the oven too hot to dry my icing.  I also find that if I am icing during the humid months (I live in Australia) and I don't use my oven to dry the icing then the same thing happens.

I don't think you need much heat at all, it seems to be more about the air drying the icing.