Going back in time a bit here to a project I completed, with the help of my then 10 yr old daughter's design, in October 2009. There are a few WIP pictures on flickr as well.
Miss Dolphin: Click image to view larger:
For this project we spent the summer collecting beads and whatnot's here and there in our travels, and online, particularly in red and white for the shirt.
I made the fortunate decision to grout the sections in different colors and to start with the white stripes. Usually I will tape off the sections before grouting but due to the crazy texture of the striped shirt I decided that I'd just go slow and tidy the edges using a toothpick after. Really glad on this choice because the slop of sanded grout on one particular type of red square bead scrubbed the color off those beads, yikes!! The project was salvaged with a short delay while I sought out replacements in a similar size and color.
Here are the offending beads after removal from the project:
I had to replace one purple bead as well in the beach ball during the grouting process. Not sure which store the problem beads were purchased from. Because of the quantity I have, I think it was a chain big-box store rather than a smaller bead store.
The Lesson- TEST your materials before use. Another mosaic blogger, TileMosaicGirl, had a similar experience with red glass gems and blogged about it here: photo slideshow and her experiment. She tested the materials both by scrubbing with grout and with sandpaper. She found that the sandpaper method was quite effective to test if the color would withstand grouting so in the future I plan to also test my materials this way.