Sunset Breads book suggests in a recipe for Sourdough
French Bread (p91 in my copy dated 1991)
1 a tray of biling water in the oven to provide steam.
2 a corstarch mixture is brushed over the crust, after
slashing, just before baking at 400F.
Brush again with the mixture after 10 mins for a large loaf
(7 mins for a small loaf) and continue baking until the loaf is
golden and sounds hollow when tapped.
Brushing mixture:
1 teaspoon cornstarch (cornflour in Australia)
4 fluid oz water
Hat to boiling, stirring, so it thickens. Cool slightly.
Jay