Keep stirring while the sauce comes to the boil and it will gradually thicken.

When it was finished there were two gene spheres with nucleus membranes gradually thickening around them.

The floes gradually thickened, packing tighter until at last we could go no farther.

She gradually thickened it and brought it up to blend into the curve.

She had led ; Bounder the entire distance, tumbling to the ground more than once in the gradually thickening storm.

Worse than this, a heavy graying mistiness was once again seeping into view in gradually thickening amounts.

They will gradually thicken and get very white as you beat in air bubbles.

Grant remembered that Jupiter's atmosphere gradually thickened until it became liquid, with no clear demarkation between air and sea.

The meal will gradually thicken and start to pop with surface bubbles (be careful of splatters).

The accompaniment then gradually thickens in texture and voice as the theme reaches its climax.