Making a concrete coffee table

Coffee tables are arguably the most important piece of furniture in a living room. They hold much more than coffee, and are a centerpiece around which the most intimate kind of socialising happens.

Read on to see how to make one out of concrete.

Finished concrete coffee table, weighing around 100 kilograms.

After some napkin math, I decided on the measures. The calculation was I needed around 5 bags of cement. I was exactly right.

Mold assembly

Putting some stuff together.

For projects like this you usually want to go with melamine wood (white boards on the upper pictures). It’s not really wood though, it’s just diced wooden garbage mashed back together into a solid shape and covered with a smooth layer. It’s cheap, easy to cut, and most importantly, doesn’t bend when wet.

I didn’t have enough melamine, so I used some other, “normal” wood that was laying around. I knew this wood would bend after getting in contact with wet concrete. I was just hoping the concrete would harden fast enough, which fortunately it did.

If you plan on making a reusable mold like this, make sure to use melamine wood only.

Pouring in the concrete

Action time.

I used a cement mix (with sand aggregate already added) and poured it into the wooden enclosure.

With concrete, clamps are your friends. Always.

Dismantling

Aah, always the best part.

After two days it was time to take the mold apart. I didn’t do a particular good job with getting rid of the air bubbles, and since I was aiming for a smooth surface, I needed to fill the gaps with slurry (3rd picture below).

Slurry is a term for cement paste mixed with a chemical that helps it bond with the already dry concrete.

Polishing

For the purpose of polishing I got myself a simple wet concrete polisher from eBay. The polisher uses diamond pads with different grits (you switch them from lower to higher numbers).

The polishing process is done on a watery surface because that way it’s more efficient and does less damage to the pads. It also prevents toxic concrete dust from entering your lungs and turning them into a stone.

Finalizing and staining

After polishing, this is how the table looked.

At this point the table needs to be stained with a protective liquid that prevents the concrete from soaking up spilled wine and whisky.

It was a bad decision to stain it with a brush, because brushmarks are seen under some angles in bright light. For mark-less coating, it’s better to use a dense roller.

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