Some bowling balls are made of a material that expands and contracts in the weather, no matter what you do to it. Others have no problem at all. You can re-grout it-just do another coat of grout, but Im not sure how sealer will affect that process.
unless you make your BB from styrofoam covered with mortar,they are best treated as temporary objects, to last a few years, because of the uncertainty with them. some ppl have great luck, others not.

anneinva,
I apologize for going on a tangent since I don't have anything to add to what wacky said- for our future projects:
I wonder if there is a way to tell what kind of bb you have? A test to do over a winter for example. I'm also thinking that perhaps just ge ii silicone holding stuff and no grout (which many of the junkers do) might last through slight expansions.
Kathy

I THINK altho I am not certain the older balls are the better ones-the newer ones are more plasticky and expand. You would be better off to simply buy a styrofoam ball and thinset it then mosaic. and I am of the mind that ge11 is best since it flexes and isnt rigid. and also-a bonus-If you use styrofom for ball-it will float when you are done!

NO really! A floating mosaic ball. That would be a wonder.

I have 3 candlepin bowling balls that I got at a yard sale. I was thinking of mosaicing them, but maybe I'll just use silicone and glue pennies or some such to them.

Kathy

I tried to find some pics-people have posted on FB after they did them, but I cant remember who posted. But yes, they will float. and the silicone and pennies idea is great.

I found one!

Here is a link that might be useful: floating mosaic sphere

Some time ago I read there was a gloss grout sealer at Home Depot. I bought TileLab Gloss Sealer & Finish but now realize it is for sealing porous tile. Will this work as grout sealer?

Yes, I've used it to seal my grout.

Thanks, I don't post often but can always count on help fast. Did go ahead and use it on a lazy susan this afternoon and like the look.