"Can I put them in the machine?" It's a question I am often asked. The answer isn't as straight forward as yes or no.
Traditionally, the paints used for glass have not tested well in the dishwasher. Sometimes, it holds up well for a wash or two but in time the paint finish breaks down and begins to wear away. Worse, The first wash will take a large portion of the paint away leaving the glassware unusable.
There is a new paint product on the market. Pebeo Vitrea 160 Glass Paints, claim to be dishwasher safe.
"After baking, colours are dishwasher safe (following recommendations) and resistant to detergents and common solvents. Only the areas not intended to be put in contact with food must be decorated." ..." So, although they're labeled non-toxic, do not allow food or beverages to come into contact with the painted surfaces."
I scoured the internet and couldn't find what the recommendations for dishwasher safety were, so I did my own testing of the Pebeo Vitrea 160 product. I don't want to bore you with technical details. Suffice to say, there is a difference in the look, feel and application of the product. I painted two wine glasses with the same design. One, I washed by hand and one, in my dishwasher. It ran with full hot water, no cold at all, glass on the top rack. Twice.
See if you can find the difference.
This photo is not retouched. Honestly, I couldn't find any fault with the paint. Admittedly, I only ran it through one more time after the initial two. Hardly, a rough test but nonetheless, one looks as good as the other.
So why isn't all glass painted with it? There's a variety of reasons.
The paints have a "glow" about them. They are translucent, which is to say you can see through the colour. That aspect has it's virtues but it's not always the look you are going for.
There is a definite difference is feel as mentioned previously. The artist would need to "re-learn" their style with a new product. There is a decisive cost difference as well. While neither is inexpensive, the new product does come with a new product price tag.
From the