Glassing Question

[Seacraft84]

Can you glass over glass or cabosil within 24 hours without sanding?
Basically I am going to cabosil the deck down Saturday afternoon and then glass the floor Sunday. Should I sand prior. I was always told you could lay glass on glass within 24 hours without sanding.
Thanks

[shine]

assuming your using epoxy, but it mostly applies to polyester as well.....

as a general rule of thumb, you can go "wet on wet" with epoxy within 24 hours and still have a primary/chemical bond. But after 24 hours the epoxy normally pretty hard and mostly cured, so your bond will be mostly a secondary/mechanical bond - if the surface is slick/smooth, then there is isn't much for the next layer to latch on to

However, as the prior layer cures, the amount of primary bond available decreases as time goes on.

Another concern (with epoxy) is blush, if you using a resin that blushes then I always wipe down with solvent then rough it up.

It takes so little time to rough up a surface and ensure a good secondary bond, why not do it and be safe? Unless the previous layer is still soft/tacky, I always rough it up a bit.

Straight cabosil/silica for bedding or fillet putty can be a brittle - I would recommend using another filler with the cabosil/silica, something with fibers: cotton fibers, glass fibers,wood flour, etc

[Seacraft84]

Thanks shine. I will look into getting some glass fibers to mix in with the cabosil. I am using polyester for almost everthing except fairing compounds and small odds and ends. I guess I will look at it in the morning and if the cabosil is some what tacky I will just start glassing, but if not I will rough it up some. Temp here today will be around 55 and tonight in the low 40s. Of course I can get my carport up to about 70-75 with the heaters, but I try not to run them all night while I am sleeping. Tomorrow will be almost 60 and sunny so it should be a good day to glass the floor.