WHY did some glass plate I painted turned milky when baking the paint?


So, I am making ForeverFlowers using vintage glass and plates. Some of my glass or even crystal I paint to add some colors.

Usually, I bake on the paint by placing the products into a cold oven, turning it to 350, and bake it for about 35 minutes after temperature is reached. I then turn off the oven and let my work cool down slowly in the oven.

One of my painted plates turned milky and I had to brush off some fine dust with a toothbrush. Still, it remains milky.

Could this be a lead crystal plate?

Any clue at all before putting my next batch to bake?

Much gratitude for suggestions.

q why did some glass plate i painted turned milky when baking the paint

The glass here used to be clear before baking like the other flower you can see

q why did some glass plate i painted turned milky when baking the paint
  11 answers
  • William William on Mar 29, 2020

    Yep it's possible the plate was leaded glass. The fine dust probably was lead oxide from the baking. If you wet the plate with water does the haze go away? If so you can try a small area, coat it with poly or mod podge and see if the haze goes away.

    • Brig Brig on Mar 29, 2020

      Gratitude for confirming my suspicions. I actually liked this one plate being milky. I just want to make sure it doesn't happen by accident again. I wonder how I can identify lead crystal prior to baking?

  • Hi there. I would say that you sound very experienced. I would venture to guess that if you've painted with this technique and these paints before and didn't end up with the milky look, then yes, it's probably what you suspect. I don't really have any suggestions, I'm sorry, but that must be very frustrating. I peeked on the internet and don't see any posts on it.

  • Betsy Betsy on Mar 29, 2020

    Hi Brig: I agree with William. In order to tell if your item is lead crystal, tap It with a Metal Utensil. The easiest way to identify lead crystal is by tapping it gently with a knife—if it makes a drawn-out chiming sound, chances are that it's lead crystal. Regular glass tends to make a duller, briefer sound when struck.

    Lead crystal is blown and cut by the hand whereas crystals are machine made. As the lead crystals are hand made, it has added brilliance and sharp facets. On the other hand, the crystals have rounded edges.

    Here is a site that talks about the differences:


  • Agnes Chrzanowska Agnes Chrzanowska on Mar 30, 2020

    I think because it did have some lead ingridient

  • Beth Beth on Mar 30, 2020

    You've gotten some good advice here. There are various hazards to watch out for with vintage. Here's a good resource on other hazards in old dishes to watch out for: epa.gov/radtown/radioactivity-antiques

  • Johnavallance82 Johnavallance82 on Mar 30, 2020

    Hello Brig,

    The piece you show in your picture is obviously Cut glass crystal! You can tell by design and you could also tell be feeling the item where it has been cut on the wheel the design will be sharp, unlike moulded glass that will be smoother to the touch. Moulded glass vary often has a seam too. If it has a design or a pontil on the base, then it is cristal...............Hope that helps

  • Brig Brig on Mar 31, 2020

    Gratitude to all

  • Beautiful work!! I really like your milky accident too :)

  • You might contact the manufacturer of the paint as they should know.

  • Deb K Deb K on Apr 05, 2020

    Hello Brig, I am guessing that you know what you are talking about, it is likely the lead that turn ed the paint milky once heated. Beautiful work!!

  • Brig Brig on Apr 30, 2020

     Thank you to all