Q&A Monday ~ cracking the base of Glass On Glass mosaics

Subject: mosaic adhesive on Glass on Glass mosaics

 
After being being asked by a customer about the heat activated mosaic glue sheets, we tried them with "glass on glass" using the GNA restover restoration glass & glass tiles.  These were heated both by the heat gun & your "patented heater" & both resulted in moderate to poor adhesion with the back glass being cracked all 3 times.....  We've gone back to using the old standard "Weldbond".  Neither of these were more than 2 ft sq in surface area.  Is this a common thing?  I am reluctant to push this product after my bad luck, any suggestions?

 P

14" round Glass on Glass (GOG) mosaic created with stained glass on recycled window glass
with No Days Groutless Mosaic Adhesive. The edge of the glass base was wrapped with
zinc edge came and soldered together with wire hangers.

Hi, P~

 I'm sorry to hear that you're having problems with the adhesive on glass on glass (GOG) mosaics. Since it is a heat set adhesive, using the adhesive on larger sheets of glass can result in cracking with uneven heating. Glass can thermal shock and crack if different parts of the window are heated too quickly. I've attached a photo of one of the GOG mosaics that I've been working on lately. These are 14" round on plate glass (recycled window panes). To heat these, I bring the whole thing up to temperature in the kiln or oven before heating with a heat gun. This ensures that the glass is all the same temperature and evenly heated. In the oven, I'll set the temperature to 200 degrees and put the piece in while the oven is room temp. 10-15 minutes later, I can remove it to an insulated work surface (I use homosote board) and continue to heat with a heat gun to move my pieces into place and push down on them to ensure good contact with the plate glass below. (In the kiln, I set the temp a bit higher so I don't have to wait so long. The kiln shelves steal a lot of the heat away from the glass.)

I'm curious to know if the curing station that you're using is as big as the glass you're building on. If it is, you shouldn't be having problems. However, if it doesn't cover the whole piece of glass, then I could see it thermal shocking. Also, what kind of surface are you heating on?

I've linked to the following blog post in hopes of addressing your other issue of poor adhesion. If the pieces of glass that you're working with have lots of texture, then there may be few points of adhesion. The surface area of the pieces that are actually adhered may be too small. Also, if the base piece of glass doesn't reach 160ºF (70ºC), then that would result in pop-offs, as well.

Do you happen to have any pictures of the failures/cracked glass?

Does this help to answer any of your questions or make sense?
Let me know if it doesn't make sense.

Carrie Strope Sohayda

---

No Days Instructor and Support Carrie Strope Sohayda

Hi, there! Carrie, here... Not only do I travel the country teaching folks how to use No Days adhesives (and other techniques), but I also answer customer support emails about using No Days. So, if you're having an issue with the adhesives, chances are good that I'll be answering your questions! Since I get so many good questions, I thought it might be a great learning opportunity for people that may be having some of the same issues but haven't thought to email us. Don't worry, I'll keep the emails anonymous! Also, don't forget that we've got a lot of really fabulous videos (I put those together, too...) on our YouTube channel. So for those of you who are visual learners (umm...we're visual artists, right?), you may want to check them out! If you've got questions, feel free to contact us at info@streuter.com.