Hi everyone,
We just finished our concrete countertops and they came out great–2″ thick, lots of curves and insets, and I’m told by my better half that the colour is “just right”. Only one niggling detail… Watermarks. Under glasses, dishes and stray water droplets near the sink. They start out looking milky and leave a ring around the edge of the watermark when they dry out.
The finish is satin water based urethane over 2 part epoxy. Is there anything I can do to reduce watermarks now that this finish has been applied? I’ve been searching through this forum and others for comments regarding watermarks on urethane, with no success. Would an oil based urethane over the water base help? Not worried about being “food safe” poly, I’m pretty convinced that oil based urethane is safe after it cures.
Any input or advice would be greatly appreciated.
Thanks in advance,
Pete
Replies
I don't know that much about concrete countertops but the epoxy should be enough and impervious to water marks. you're probably getting the water marks from the water based poly.
Can you sand that off and re-coat with epoxy?
Agree with Mrsql. If there were watermarks on the slab before you put the finish on then that is where your problem is, on the concrete. If the watermarks occur when you put a glass on the finish or when something wet sits on top of it then it is probably the top coating.
I just finished a countertop (not concrete) and put on about 10 coats of Oxford brand water based laquer. rubbed the finish out and installed. I thought the stuff was pretty much bullet proof. I guess I thought wrong. We left a wet glass on it and it did a funny ring where the glass was. Come back a few hours later and it was gone.
So, to make sure I'm reading you correctly... you're getting water marks on a top coat of waterborne poly? No mystery there... the only way you can remedy that is a different topcoat it seems to me.
PaulB
The watermarks are on/in the top coat of of water based poly, not in the epoxy or the concrete. I've applied water based poly to wood (beech) before and don't get watermarks (different brand, can't remember which... let's call it Brand X).
I don' think there's any "magic water based poly" for concrete countertops (despite what the concrete supply fellows told us) since it needed the epoxy as a primer to adhere to. Since I didn't have watermarks with the Brand X poly on the beech, do you think it's worth trying Brand X over the existing poly on the countertops? I'd like to avoid stripping and resealing, if possible. I'm thinking if I scuff sand before applying Brand X it should bond OK.
Thanks everyone,
Pete
I've made a couple concrete countertops with WB poly (even the ones sold specifically for concrete) and they had the problem you describe, although IIRC the rings did go away after they completely dried out. I have my own theories about why it is, but IMHO the bottom line is that's your problem. One way or thother you need a different top coat, I don't think any of the waterborne poly finishes are going to work... PaulB
I agree, it looks like the top coat is the problem. The concrete folks we bought our supplies from reccommended the WB poly since it's more scratch resistant that the epoxy. The epoxy is basically a primer for the WB poly and worked really well---self levelling, filling in small pinholes, etc. Friends with concrete countertops recommended using the WB poly over the epoxy also, since their bare epoxy top coat tended to scratch up.
Does anyone know if it's possible to apply an oil based poly over the WB poly? I've done a search and can't find answers. Off the top I think it will work if I scuff coat and the WB poly has completely cured, but I'd like a better gut feel before starting a corner 'test piece'.
I'm not sure of the end look you're trying for but once I did one where I used a clear epoxy intended for bar tops. It was called "Build 50"... I think the coating is 50mils thick. Very scratch resistant and waterclear. Very pricey but does a great job. No clue about applying over WB poly, but I imagine you could call the manufacturer. Hope this helps...
PaulB
What is the epoxy finish you used?
I did counters for a client about 3 years ago and they want to go to a solid finish rather than tile sealer and wax.
"Research is what I'm doing when I don't know what I'm doing..."
The watermarks are there so no one can make a 'counterfit' copy of yours.
Sorry couldnt resist
I'd wait a while to see if the poly finishes curing. It may get better with time.