When you put the thinset on did you score it before you put the tiles, etc on? It may be because there wasn't a whole lot for it to adhere to. I don't know if the wood being painted would cause any problems especially if it is sticking to the wood. Course I'm just guessing, don't really know for sure what caused it unless it was too dry.

Donna in Florida

I think I would have sanded the wood, then sealed it before adding thinset. Another good idea is to add an adhesive to the thinset, such as weldbond.

You can use Weldbond in place of the thinset. You can also use Weldbond to seal the wood. One part Weldbond and five parts water is the formula I use. It works great.

If the thinset sticks just fine to the finial, then how you treated the wood prior to covering it is not the issue. What was your procedure? Did you coat the finials and then let the thinset dry before applying tiles? If so, did you use more thinset to place the tiles? Or did you just use thinset on the backs of the tiles and apply them directly to the wood? I just can't imagine what would make the tiles pop off of the thinset. Could your thinset have been too wet?

I've had this same thing happen to me once and all I could figure was that my glass wasn't clean - oily. At first I thought it might be that the water was drawn out too quick but like you , the thinset stayed on my substrate and just the glass pulled off. and just a handful from the same region. Plus I was prewetting my concrete column as I worked to avoid the soak up problem

Thanks for your replies. Sabrinacarr- the way I applied was simply to slather on thinset in a small area and apply the tiles to that area, then move to another area and do the same. Nicethyme- I used different tiles on different finials and one of the tiles I used was one that I had used on a sealed ceramic pot and they stuck just fine. So I don't think it was an oily problem this time, although I'm going to remember that, because I don't always clean my tiles well before using them! Just take the plates from my garage stash, wipe the dust and start nipping! I'm so bummed about these finials because they were really cute, but they took a while because the pieces were pretty tiny. I was going to put them on top of stakes and put them in amongst the flowers in the garden. Since they're for outdoors, that's why I was using thinset vs weldbond. So, I think I'll clear one off, seal it and try again. But just one at a time and see how that works. Thanks everyone!