Instructables
Picture of DIY CONCRETE:: Coasters + Trivets
This instructable will show you a quick and easy way to make concrete coasters and trivets from the lids of plastic containers. The lids used in this Instructable are from plastic tupperware found in the top shelf of the dollar store. Look for lids that are not too shallow or you might have problems with the concrete breaking.

There are four steps in this Instructable - Preparing the Lid, Mixing and Pouring Concrete, Grinding and De-molding, Sealing and Finishing.

Materials: Concrete Mixing:
  • Bucket
  • Water
  • Particle Mask
  • Rubber Gloves
Tools / Supplies:

Step 1: Preparing the Lid

A good lid for this project:
  • Coaster Size = 4+ inch
  • Trivet Size = 6+ inch
  • Flexible Plastic
  • Plastic that is durable enough to be re-used
  • Watertight 
  • At least 1/4 inch thick
  • Not threaded inside (so concrete can be released from the lid without having to break it off)
  • No logos
  • Free / Cheap
Less than Ideal:
  • Paper / Cardboard
  • Thinner than 1/4 inch
  • Undercuts / Threads / Deep Logos
  • Thin plastic is OK for one casting, but can't be reused easily.
Prepare the Lid for Casting:
  • Clean the lids with soapy water using something that won't scratch, like a 100% cotton cloth.
Decorating Concrete:
  • Use a light mist of spray adhesive in the lid if you want to include decorative aggregate, crushed glass, or any kind of inlays.   
  • Use crushed glass and decorative aggregate that complements the color of the concrete.
  • Rubber stamps can be fixed to the form with spray adhesive and removed after the concrete has cured, leaving the rubber stamp pattern as a relief in the surface.
 
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MacGyverG2 months ago

How do you hold the coaster in place during the orbital grinder phase? I haven't tried this yet, but in my mind I see this being flung off the table at some extremely high speeds.

CHENG Concrete (author)  MacGyverG2 months ago

Yes, this can be a problem. If you make a frame to go around the piece, from something like 1/4" wood, that help keep the piece from moving around. I usually just put the coaster on a piece of pink foam, and the coaster grabs into the foam enough that it doesn't fly away. When the piece is a bit thicker, it's pretty easy to hold in place with one hand while the other is holding the polisher. I've never had a piece fly away like you might think, they usually just spin in place.

ardnon1 year ago
These are great. I know I don't really need denatured alcohol for this project, but does anyone know where it is available in Canada? Having a really hard time finding any for other projects...
Denatured alcohol is just pure grain alcohol, made unpotable (toxic) by the addition of wood alcohol. In this way it can be sold in hardware stored without subjection to liquor tax.
CHENG Concrete (author)  ardnon1 year ago
Rubbing alcohol will work too!
shazni1 year ago
Please ...may I know the exact names for the discs I need to buy if I want to grind , polish and cut or what ever with concreat? I have an angle grinder with only a sanding pad and aluminum cutting disc. I would really like some help in this.
CHENG Concrete (author)  shazni1 year ago
There are a lot of pads out there for polishing concrete, some of them come from the granite industry, others are designed specifically for concrete, like the pads I've listed below. A rigid pad will be harder for a beginner to use, because you can accidentally dig into the concrete if you're not holding it flat. A softer pad is more forgiving and works well if the piece has contours. There's no industry standard for grit size, so you want to try and stick to one manufacturer rather than mixing and matching a set. For grinding deep into concrete to expose the aggregate, you'll start with a 50 grit pad, to just expose the fine sand you might start with a 400. The progression is usually like this: 50, 100, 200, 400, 800, 1500. This will produce a nice shine on concrete and there's usually no reason to go any higher. Even glass inlays will be pretty well polished at 1500.

Here's a link to a good 5" orbital polisher we use a LOT in our training: Alpha VSP-120
And a link to a soft pad set: 5" Diamond Wet Polishing Pads
And a link to a rigid pad set: 4 - Step Concrete Polishing System

The VSP-120 is a variable speed polisher, water-fed, up to 4000 RPM. It plugs into a standard wall socket and screws onto a garden hose. The pads are not designed to be used over about 4000 RPM. Above 4000 RPM the resin will start to melt and ruin the pad. Most of the pads out there designed to be used at a lower speed, not with a high speed angle grinder.

Alpha Tools recently came out with a wet / dry polishing pad system that is designed to be used up to 10000 RPM and will work on a high speed angle grinder. They sell a hub and a shroud that should fit most angle grinders out there. This is a real nice setup, and when used with a HEPA vacuum, there's no dust at all.

The important thing to know about diamond polishing pads is that if you buy cheap pads, they won't cut as well or last as long as the more expensive / quality pads. Diamonds are doing the cutting, and the cheaper pads simply use fewer diamonds.

If you're really doing a lot of concrete polishing, you're probably using a pneumatic polisher, hooked up to a huge air compressor.

For cutting and grinding, there are these cutting blades and grinding / shaping wheels that will work with an angle grinder.

I'd recommend a variable speed polisher like the VSP-120 and a set of soft pads. I like the soft pads because they're hook and loop backed and really quick to change out.

Hope this helps!
Thanks a lot!! yes it really helps :-)
they look like the lids from containers that you get from a deli ( for things like pasta salad).
thanks for they help...but what i ment was the disc pads that is used in the angle grinder to grind concrete. does anyone know exactly what is necessary??
inspiring!
nice
nice work
Amazing job!
Cool! So fancy looking :)