Carved In Stone Part 2

OK, here is the countertop after the form was dropped out and the styrofoam block out for the sink pulled out. I let the concrete cure for 4 days before removing anything and it's not a bad idea to wait 7 days. I also kept a wet towel over the slab for mot of that time to help the concrete cure. As you can guess, I made the blockout from rigid styrofoam just so it is easy to get out once it is encased in the concrete. You can cut it up if you have to but being rigid it does not give against the weight of the concrete. I traced the outermost diameter of the sink shape and then came in about 3/4" all the way around to get the size for the blockout. That leaves the sink edge resting on about 3/4" of concrete all around. The sink sits off to one side of the countertop but is centered over the plumbing stub outs. Now, I made another mistake doing this. I did not notice until later that this makes the sink slightly off-center the two light fixtures, thus any mirror hung between the fixtures will not center up over the sink. This is what happens when you let it take so long to complete a project: you forget what your original thoughts and plans were on the project and you get in such a hurry to finish eventually that you don't think about stuff like that. So, I'm going to have to move one light fixture out slightly to correct this. No big deal but still aggravating.
I also poured a two-part backsplash for this countertop but did not get photos of that process.

This sink, along with 2 more, were salvaged from one of the hospital remodels we did a couple of years ago. They are practically brand new Kohler sinks and came with the fixtures and all. Now, I hate those fixtures and will replace this one shortly but for now, this is what I got. Now, when I wrecked the form off it left a sharp edge on the top of the slab but there is an easy way to remedy that. The bottom edge was very slick and rounded due to the silicone caulk I ran in that crack.

A 4" side grinder is one of the best tool investments you can make. They make an endless variety of discs for these things for use on everything from wood to concrete. They are not just for metal anymore! I simply used an 80 grit sanding disc but, if you want to spend the money, they make a bunch of diamond-coated discs and blades sized for these tools.

So, WETTING the edge of the concrete, I simply rounded that top edge off until I had the contour I wanted. Now, even these sanding discs will take off quite a bit if you are not careful so you have to pay attention to what you are doing. You don't have to wet the concrete but if you are working inside it's a good idea. So is wearing a dust mask. I just kept the faucet running slightly and would periodically scoop a little water over on the edge as I passed by. Now, this does make a mess in your floor and on the walls so cover stuff that you can't just mop clean.

I then used a hair dryer and heater to dry the concrete thoroughly before applying the sealer. There are many types of sealer for concrete but I simply used a 50/50 mixture of beeswax and naturally derived linseed oil because ya'll know I try to only use natural products. For kitchen countertops, you can get a food-grade beeswax to seal those with. We have used that to seal limestone countertops and it works fine on concrete. The mixture I used darkened the slab considerably but it will lighten up some as the product cures. Either way it is fine with me. I then used silicone caulk to glue the two pieces of backsplash into place. In a couple of days I will caulk the cracks between the countertop and backsplash and against the wall. The beeswax/linseed oil is very sticky and thick at first, so you have to heat it to apply it smoothly, but it soaks in quickly and after about 30-60 minutes I wipe off the excess and buff the surface. It will not make it shiny but has a nice satin finish. If you want to use concrete for a finished product you need to be able to accept a certain amount of surface variation. It will not look like Corian or limestone. It has veins and mottling and even some tiny surface cracks so you have to accept that. Now, I don't say that to make excuses for poor workmanship; it is just the material that you are working with.
I was kinda surprised at how many of you are wanting to do concrete countertops so I will do another post on tools and more specifics on how to finish the concrete. I will tell you this, concrete is a wonderful material but it is very unforgiving. You need to practice on some things before you start your real project if you don't have much experience. It takes a real touch and lots of experience to be able to get that hard, slick finish and once the concrete starts 'going' there is not much you can do to stop it. There are some tricks and such and I will try to give ya'll some more info on that. If you have any specific questions or something I didn't even show, please ask.