Tiles I like for kitchen need sealing. Likely to be a problem?

[ThrowAChickenInTheAir]

I've found some crackle glaze tiles for my kitchen but apparently they need sealing.

We've never had to do this before. Does it alter the appearance? Will it need to be done again?

Thoughts much appreciated

We just did this- it was really easy and tiles looked the same. Had to do two coats but that's it- they are in our bathroom so we can easily tell that it's worked as the water isn't getting in to them.

Thanks Olivia! I am reassured