One of the most disappointing things about fusing bottles is opening the kiln and finding that unusually colored bottle was painted, and all the paint has burned off.  So, how do you tell if a bottle is painted?  Here are 3 quick tips. (This is the bottle itself.)

 

1.  Multi-color mass produced bottles are pretty much non existent.   I'm sure that there are some hand blown bottles out there that are multi color, but I'm talking about factory made stuff.  For example, here are two perfume bottles (contributed by a lovely reader, thank you!)  One is blue on top fading to green on the bottom, and one is clear fading to frosted pale pink.  

 

These guys are painted.  BUT! don't discount them too quickly, they are both unusual shapes, and when cut into slices will make amazing jewelry pieces.  There are a number of liquor bottles that have an ombre finish, know that the final fused result will need to be tested.  It may be best to use them for a cold project, like a bird feeder or trinket box.

 

Here's another type of painted bottle to watch out for, I was given this pretty cobalt bottle and decided to cut it up to make oval donuts.

 

When I took the top off, I found this:

 

2.  Color that doesn't extend all the way to the rim is an indicator that the bottle is painted. 

 

3. You can scratch or scrape the color with a razor.  Sure enough, the paint scrapes right off.