Deep Pour Epoxy Table Cupping

If your deep pour river table or surface is cupping with both wood slabs being pulled up on the outside edges, this is due to the slight shrinkage that epoxy has as it cures.

When pouring a river table, you want to be sure that you are not pouring an excess amount of epoxy on the top of the surface after the river is filled. You only want to slightly over-fill the river portion to account for shrinkage, when overpouring most of the surface the epoxy will shrink causing it to pull the slabs inwards, and with no epoxy on the bottom to keep it from moving it will pull the edges up slightly causing it to cup.

The best way to avoid this is to pre-flatten your slabs before using the epoxy, this will flatten any voids you may have on the bottom and tops but also will help reduce the amount of epoxy being used due to unnecessary filling. After this you will only want to slightly overfill the river area, you may also place a bead dam of silicone caulk just a few inches outside of the river section to help keep it from flowing further out onto the slabs.

If you do end up with cupping your best option is to take it to a woodworking shop with a CNC machine and have them pull the edges down to flatten the table and slowly route away the excess epoxy until you only have the bare wood and the river portion filled. Then you can go back and finish it how you like with a stain or oil finish.