How well do umbrellas block UV

[CrackMagic]

Will an umbrella be sufficient to block sunlight UV and stop premature curing or will I need an actual UV shield?

[gt_repair]

You will still need a towel or UV shield. I use a towel to rap the injector. I also use an umbrella on hot days to cool the W/S so I can work it.

[GlassStarz]

Uv reflects so even though the Umbrella will block the dirrect UV you are still gonna get some unwanted UV if you dont cover it up