Dutch Crunch topping failure – Why?

Yesterday, I made Peter Reinhart’s Vienna bread with the dutch crunch topping. I pretty much followed the directions exactly. I mixed up the dutch crunch paste (using rice flour) to a very thick consistency and applied it moments after the final shaping in an effort to get the most dramatic mottling effect. It was a bit too thick in retrospect – I couldn’t brush it on. Rather, I had to spread it on with my fingers.

Then I let the bread proof for 90 minutes with the paste on top. Everything seemed fine, but the final product was not as expected. The dutch crunch topping barely browned at all. It was several shades paler than the crust itself, as you can see in the photo below. I believe the topping should come out darker than the crust. Furthermore, the flavor was terrible. It tasted like chalk. Any idea what could have caused this? Was there not enough yeast activity in the topping? Was it just too thick?