1946 is a vintage I know fairly well, as I've been lucky enough to drink it on a dozen occasions. I can tell you that the bottle of the 1946 Castillo Ygay Blanco Gran Reserva Especial was not the best I've had. The vintage is really unheard of in Rioja (I don't know any other wine from that year) and curiously enough, the winery seems to have quite a lot of data about this wine: it's said to have been a blend of 91% Viura, 7% Malvasía Riojana and 2% Garnacha Blanca. This is the only vintage I know where they mention Garnacha, but you know how varietal percentages are not always accurate, and even less so with such an old wine. It fermented in old 18,000-liter oak vats where it was kept for 15 months, and then slowly matured for 222 months (that's 18.5 years!) in well-seasoned, neutral American oak barrels averaging 25 years old. It was bottled in March 1967 and released in 1973.
A superb bottle I drank pushed me to write a 1,300+ word essay on a single bottle of wine in 2009, so the wine can be truly inspiring. This bottle was a little more advanced than the others tasted with this (as well as previous ones from this same vintage). It was the only wine that didn't come from the winery's library; it was purchased from a private collector. It had notes of iron and earth that made me think of a slow oxidation, perhaps in a slightly warmer cellar. You know with old wines there are no great vintages, there are great bottles. And unfortunately this was not one.
The analysis of the bottle tasted showed 12.67% alcohol, 2.94 pH, 7.19 grams of tartaric acid per liter, 0.85 grams of volatile acidity and 120 milligrams of sulfur.