Now before we start pouring, it is extremely important that you work on a perfectly smooth surface.
We used Butterfield flat-mix liquid color blend. This bench blend is glass fiber reinforced, polymer modified, self-consolidating and has a compressive strength of 11,000 psi. We chose this over rain concrete as it is much less porous and therefore much less stain resistant and is 3 times stronger which allows us to pour a thinner plate. If you use traditional concrete mix 1 part Portland cement, 2 parts sand, 2 parts pea gravel or 1/4 ”crushed washed gravel. If using a polymer modified blend, use bag instructions.
To eliminate bubbles and create a more flawless finish, we will use a texturing gun to spray our first two layers. To do this, you must remove the stones and fiberglass from your concrete powder. Now it's time to pour the rest of the mold that you don't have to strain through the mixture for this part. Simply mix the flat mixture with the liquid poly until the desired texture is achieved. It should resemble the texture of the oatmeal.
If you use polymer-modified concrete, you can make your mold as thin as 3/4 ″ thick (as we did). If you are using traditional concrete mix, make it at least 1
Use your fingers to agitate and shake the mixture to release air bubbles. Now place your 3/4 inch styrofoam in the center of the mold and leave about 2 ”around the outside. The styrofoam should be in line with the top of the mold.
Then the foam would screw down to prevent it from flowing as we pour the edges. Now pour the edges and adjutant with your fingers again.
Be careful not to fill the mold otherwise you will need to sand it down which risks damaging the edges.
Let mold sit for 48 hours with traditional blend or as little as 3 hours with polymer modified blend.