Previous Post: Gold Concrete Bar Rubber Mold
did some color tests to try and find a good color to make concrete look like gold. this is yellow base pigment in rapid set concrete mix. in the first test I used a 9% pigment load, which was too yellow.
1. 2 lbs. 1% load = 3.17 grams
2. 2 lbs. 2% load = 6.35 grams
3. 2 lbs. 3% load = 9 grams
4. 2 lbs. 4% load = 12.7 grams
5. 2 lbs. 6% load = 19 grams
6. 2 lbs. = no pigment
settled on a 6% pigment loading and started making the gold bars.
first I spray the rubber molds with mold release and then brush gold lustre pigment into them. the release helps the gold stick to the mold so it will be captured by the concrete and show up on the surface.
since I have to make 30 of these, I’m using rapid-set so I can demold the next day. first I place a little bit in the mold and vibrate it so it fills in the details. Then add a bit more and vibrate, add a bit more, vibrate, add more and vibrate, fill the mold and vibrate so it settles out. Filling it in stages and vibrating helps minimize air bubbles on the sides, but too much vibration causes the gold powder to churn into the concrete instead of showing up on the surface, so it’s a fine balance.
after the molds are filled the concrete is troweled flat and smoothed out. cover it in plastic and then wait until the next day to remove the pieces.
first batch ready to seal. the bars are set on something so I can wipe sealer on the underside.
the sealer will enhance the color a little bit, but I’m also putting the gold lustre pigment in the sealer so the pieces will have more sparkle. two coats of tk6 gloss nanocoat is good enough for this project. with the bars sealed, we don’t have to worry about handling them and they should look good for a long time.
Final mix – 10 lbs. mix, 64 grams pigment, 22 oz. water – makes 2 bars
about 12 more to go before I’m finished. thanks RC for the fun project!