I am an artist from Italy.
I am looking for high-quality, thick paper with a metallic look that I can use with gouache - true gouache, not acrylics or oil. I am terrible at gilding, but I need an even, shining surface like that one gets after burnishing real gold foil. I have got an idea that can profit from any background, because it'd be a series of paintings. I am used to Canson Héritage hot pressed 300 gr paper, which I use for watercolour, but, even if I could gild decently, I couldn't use it anymore because it is discontinued.
What would you suggest? What (possible) treatment of the surface before/after painting? Where to buy from Italy? How could I get samples?
Thanks.

For a smooth, even, metallic look suitable for traditional gouache, we recommend a pearlescent paper, such as Stardream, which is available in a gold color. The surface accepts gouache well and provides that uniform metallic sheen you’re looking for—without the hassle of gilding.

However, for a true gilded effect, we recommend an uncoated paper such as Colorplan, which is known for its strength and rich color range. You could work with a printer or foil specialist to pre-foil your sheets with gold or other metallics in large areas (or full coverage), giving you a burnished look to paint over. Legion as a distributor, does not sell directly, but the above papers are available across Europe through a network of mill partners.

If you’re seeking an alternative to the Canson Heritage HP, we recommend the Stonehenge Aqua HP paper. It’s a 100% cotton, premium watercolor paper available in 140lb and 275lb weights. You can find Stonehenge Aqua in central Europe through KunstPark and PetersArt in Germany or through Jackson’s Art in the UK.

Here are some links for more information:
https://legionpaper.com/stardream/
https://legionpaper.com/colorplan/
https://legionpaper.com/stonehenge-aqua/

German Distribution of Stonehenge Aqua
https://www.kunstpark-shop.de/index.php?lang=0&cl=search&searchparam=Legion
https://peters-art.de/Legion-Stonehenge-Aqua-White-Block-300g-m/11635

Jackson’s in the UK:
https://www.jacksonsart.com/en-us/brands/legion

Thanks. Via Instagram I got a reply from Legionpaper telling me to try UniLustre, but I don't know where to buy it. I guess I have to ask https://unifoil.com.

I see Stardream does not reach 300 gr and I fear it may buckle. I will ask directly the maker to get a sample to make a test.
Even if I understand what it is, I don't know what this pre-foil procedure is, nor how it is called in Italian, but I don't think I could easily find someone near me who does it, and I can't afford many expenses.
I can't buy easily from Jackson's, I tried in the past, but what I purchased took 40 days to reach me and I decided never to try again.
Thanks again.