Spain and Hair Appliances

Buy a plug adapter here. They don't need one over there.
Ensure your curling iron is dual voltage as they use 220.

If what you meant was a power converter, then again, buy it here so it will accept a north american plug....and you will still need the plug adapter. It might be cheaper to buy a new dual voltage curling iron. I got a nice small one for travel and it converts automatically.

Thank you for the info....could you provide specifics on what you purchased here?

1. Be sure your curling iron is dual voltage (it will note it in the writing on the side, near the UL symbol) and be sure you toggle it to the higher voltage if it doesn't automatically work on either (it'll look like a screw toggle thing on the side, one will say 110, the other 220).

2. Be sure your adapter can handle up to 250 volts and 3000 watts - this will again be written right on the adapter - they are heavy-duty adapters and are designed for heavy use appliances. If you use an adapter with improper volts and watts, you'll melt it and potentially start a fire.

Or just buy a curling iron when you arrive.

An adapter changes the shape of the plug.
A converter changes the voltage.
True, if you travel to Europe often, then you can consider buying one there, but not all locations have the same plug head. You would need a different adapter for UK from Spain, and getting a compatible one might be harder back in US.
I have this travel curling iron by Tool Science. It has some rotating feature, but it can be locked to not rotate. I also have short hair so a small barrel works best.
https://www.sallybeauty.com/hair/travel-size/rotating-travel-curling-iron/SBS-646104.html?list=Search_Results#q=tool%2Bscience%2Bcurling%2Biron&start=1

plug adapter

https://store.ricksteves.com/shop/p/european-power-adapter

Be very careful using your dual voltage appliance, though--irons in particular can get unpredictably hot and fry your hair. I used to bring a curling brush and even that didn't heat as predictably as at home.

All of this advice is good ... but I’m with every tour guide I’ve ever spoken with on this one. Frankly, no one -including you - is going to care that your hair wasn’t perfectly styled. Being on vacation is an opportunity to simplify your life and free yourself from the minutiae and fuss that weighs you down every day. Get a great haircut before you leave and invest in some simple beauty products that allow you to confidently shower, wash and go while you’re traveling. Leave the appliances at home and save yourself from lugging them around; more room for souvenirs that way! :)

Good advice from the ozone. Many European hotels these days have hair blowers to dry your new sensible haircut. Curling irons, however, are a heavy-duty appliance putting strain on a converter. If by chance your hotel room has one of those old sockets for an electric razor, do not plug anything into it. Enjoy.

I’d stay away from voltage converters and get a dual voltage curling iron here plus a plug adapter. Good advice from another post to check on the product itself that it’s marked 220, not just 110.

Then if it doesn’t work satisfactorily in Spain, go to plan B: go shopping at El Corte Ingles for a moldeador. I’ve had good luck with Babyliss and Remington brands for hair appliances in Europe. If you go to the UK, it’s easy to get a Euro/UK plug adapter.

Curling irons are not necessarily large to pack, and just me, I might not want to change hairstyles right before a vacation.