Paper
To produce a platinum-palladium print, one coats photographic paper with a platinum-palladium based emulsion. Paper selection is critical because not all paper is suitable for this medium and results vary depending on paper. Choice is entirely personal and you will find your preferences over time. I like Buxton Rag and Herschel Platinotype made by Ruscombe Paper Mill in France. Buxton is 100% cotton rag and Platinotype is 100% linen rag. Both are expensive but beautiful. I sometimes use Revere Platinum which is 100% cotton and dries flat.
A marvelous resource for paper and chemicals for platinum - palladium printing is Bostick & Sullivan, a family business that provides personal service and advice.
Here are helpful links to websites mentioned in blog posts.
https://ruscombepaper.com/uk/handmade-papers-category/paper-for-alternative-photography