How to tell parents about a tattoo?

So I have an appointment for tomorrow (monday) to get my second tattoo, and it's going to be an inner bicep tattoo. I'm eighteen, and paying it for myself but haven't really told my parents yet. I got my first one done back in the summer while visiting my friend so they couldn't have done anything if they knew beforehand, my mom was more okay with it than my dad (he really doesn't like them.) so I'm not sure about how to go about letting my dad know, I think it would be more mature to talk to him later today about it, but I'm not sure how to go about it and I don't want him to try to not let me get it, so I could just tell him afterwards but that's probably not the better idea. So what kind of things could I say when bringing it up if I talk about it beforehand?