I dont use biscuits on my worktops because you cant lift or drop the worktop when its glued together. Sometimes a final play with the scribe is needed to get them perfectly flush. The bolts are quite enough to hold them together while the silicone(clear, low modulos) cures. Dont screw the worktop down while its still wet untill the next day or the scribe might pull down too! Its happened to me!! as for the colour fill, try to keep away from this unless youve got scratches. Its too expensive and too messy. Hope this helps. Leo
I always treat any open edges of worktop, around the cut out for the sink easpecially, with a couple of coats of PVA sealer to protect it from any water damage, I then use any proprietary brand of wood glue to fix the two pieces together. The use of the clamps set into the underside of the worktop is in my mind essential but the use of biscuits less so.
I always use a waterproof wood glue as I am starting to tighten up the clamps underneath. Also I apply Colorfill to the top of the joint which when clamped up also forms a good waterproof seal. You can buy Colorfill in colours to match the worktop and it helps to disguise the join. Excess can be removed with Colorfill's solvent cleaner.