What to seal painted stones with if leaving outdoors?

[SOT3]

Could anyone advise the best thing to use to cover stones that have been decorated by children, so that they won't get spoilt when being left outside please?

I just use varnish

Sorry to be thick bit what kind of varnish exactly and where would I buy it from?

I just use an old tin of Ronseal clear varnish that I’ve got. I sure you could get some from B&Q or similar. Or if you’re just doing a few small stones clear nail varnish would do the trick.

Yes it is just a few little stones so might buy some clear nail varnish. Thanks so much for your help.

(name change fail).