There are two main types of developers that we use for Platinum/Palladium printing: Ammonium Citrate & Potassium Oxalate. AC developer gives a neutral print regardless of metal used. Oxalate developer will give the warmest print with 100% Palladium at a hot temperature. The cooler the Oxalate and the more Platinum is added into the Pt/Pd coating the more neutral-warm the print gets. For our proofing service we offer four toning combinations that you can choose per image. View the previews below to get an idea of what these toning options look like. Please note: this product is not a true Pt/Pd service! We use special Piezography curves to simulate the tonal range of whatever Platinum/Palladium print you may do with us in the future. These prints are done with Piezography ink on paper and that how we can give you a proof that is only $20/print. Actually Pt/Pd printing is way more costly as it uses precious noble metals.