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Concrete casting – first try


I’d long wanted to have a go at making “stone” pots, troughs etc – hypertufa looked awfully complicated, with getting the right ingredients and mixing them properly in the right proportions, so I thought I’d get a bag of ready-mix concrete, just-add-water-and-stir, and see how I got on with that first.

Got a very small bag (it was the only one the hardware shop did that I’d be able to carry home!) and it sat there for months: got packed in the moved, unpacked, and sat there for more months.

I was trying to find a small mixer, but “small concrete mixer” turned up ones that held 160 litres, a tad much for craft casting, at least for a beginner small scale. Then I had an idea, and bought a large wide plastic jug and a twin-blade hand-turned whisk. That should do for mixing, I thought; if it does cake mixes, it should do concrete dust and water!

All sat there for another month or so, then one day I thought, Right! Do it today or get rid of the lot. So about 7am I got ready: bearing in mind the fineness of the powder and how close I’d have to get to see what I was doing, I took no risks: put a dust mask on, and wore long sleeves tucked into rubber gloves so my skin should be protected from splashes (there were warnings on the pack).

Didn’t really know what I was going to do with it; didn’t have a mould to cast into. I had some finely sieved dirt for exactly this purpose – I’d thought about putting it into a dish, pressing something into the dirt and putting the concrete in the “mould” – I could then smooth the dirt and press something else, so I wouldn’t need a rigid mould.

I picked a shell from one of the pots and pressed that in – the dish wasn’t quite deep enough but I decided to have a go anyway; tried pressing the shell in on different sides to get different impressions.

I couldn’t see any directions on the pack for what proportion mix-water to use, so I just chucked some water in the jug and added the mix carefully, bit at a time. The only thing I didn’t think of was how to scoop the powder so had to use a spare plant-food scoop – didn’t fancy using a kitchen spoon!

I wasn’t sure whether to add water to the mix, or add the mix to water; the pack instructions implied adding it to water, so put loads of scoops in, then gave the whisk a whizz. Then loads more, whizz, then loads more … the mixture didn’t seem to be thickening much. I had a tentative grope in the jug and found that the mix was ridging up around the bottom rim where the whisk wasn’t reaching. So grabbed a barbecue stick (all that was to hand) and stirred into the corners till it felt even.

The pack said to mix to a “smooth paste” but it didn’t look very paste-y; still very runny. I didn’t want it too thick to pour, so I decided to give this a go and see how it took.

Hit a problem immediately: black holes in black dirt are very hard to see! I managed to find them, more or less, and filled the space with all the concrete I’d mixed – there was a bit much, but not too much, all things considered.

Put them in the shed to set – the pack said it was very quick-drying (compared to what?). I checked them a couple of hours later and gave one a very gentle prod, it seemed firm already, but I’d read other people’s blogs about leaving concrete for a couple of days, so I left them all day and night; forgot about them the next day.

Took them out the third day. They don’t look much like shells, or even shell-shaped! But at least the method worked, more or less (rather less than more, I think). Maybe I should have used a less fancy shell, or at least a smaller one that would have fitted all the way down; maybe I should have firmed the dirt a bit more, or damped it a bit more – and certainly should have mixed a bit less concrete, or at least not have filled the holes so much that the excess overflowed.

But still, for a first go and working totally blind, I’m not hanging my head!




There seems to be a lot of dirt embedded in the concrete: I gave them a cautious wash and a bit of a scrub, but that doesn’t seem to have improved them much. Maybe I could have added some colour to the water before mixing – it would have been rather hard to grease a hole in dirt to ensure the concrete didn’t stick!

The final results look more like stranded whales than shells, because of the overflow of extra mixture – the how-to sites say to have something in reserve to use up any excess mixture, but I didn’t think I’d mixed that much.

This was about half a pack – maybe I could have mixed it thinner, it set very fast in this concentration.

If anyone knows what the proportions should be, please share!
and any other tips?

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With this type of project you learn as you go along...
would be logical to start with much simpler shapes, while you learn about the process ...

This past fortnight, I've been ridiculously busy replacing some of my dog-run fence panels which were literally falling to pieces.

In the past, I'd only done small woodwork tasks, but have now taught myself various ways of hand-sawing etc.

You can see the first panel on my recent blog. I've now completed four panels ... the ones which were most in need of replacement .. and I'm really delighted with how they look ...

... but must now stop to catch up with other urgent tasks, such as an overgrown garden .. and then maybe return to carpentry again later this summer !

14 Jun, 2014


indeed, one can't really learn unless it's hands-on: reading books and how-to's is all very well, but you have to learn to apply the knowledge, or work out your own way of doing things. lol my prob is that | often suspect that I'm going round three sides of a square because I don't know the short cut!

I'll rush over to your blog right now

14 Jun, 2014


Yes... hands-on is certainly a good way to learn ..

I find I don't always do DIY and crafts in the 'traditional' way ...
... in fact, over the past 2 weeks, if expert carpenters had watched me making those fence panels, they would probably not have approved of my methods, but the end results seem fine.

In fact I look out on the panels from the kitchen and can't quite believe I made them and fixed them up :o) Lol.

My blog is called R I O ... Repairing It Ourselves.

Good luck with progress on your concrete shapes.

14 Jun, 2014


found it, and loved it - and you did it iwth no more tools than I have - a cordless drill-screwdriver is my only power tool. makes me want to sort my wood and find bits to work on.

Whatever works for you is valid - they've learned their ways, you've learned yours.

Old Chinese proverb, think from Con fucius: "I hear and I forget. I see and I remember. I do and I understand".

14 Jun, 2014


I like the Chinese proverb :o)

yes.. I have only a few tools ..
I prefer to use the cordless drill for drilling, and then I screw the screws in by hand.

I have some old hand tools which are 'heirlooms' ...
A few weeks ago I cleaned them ... hope to do a blog on those some time... there are a few I'm not sure of their purpose ... one or two look quite lethal .. Lol.

14 Jun, 2014


agree with Terra...keep going'll learn through your trials! :)

14 Jun, 2014


So glad you plucked up the courage and had a go Fran, the results are fine, you could use them to decorate alpine troughs if you have any.

14 Jun, 2014


You never know where it will end...there's a man near where I used to live who started making garden ornaments and eventually had to give his job up and do it full time! Apparently he will make anything you want to order! That could be you in a couple of years Fran! ;) p.s. sorry to be so little help, I've never had the urge to try anything like this myself!

14 Jun, 2014


@ TT same here - the drill can be adapted for screwdriver blades, but it's such a drag haivng to wind it all the way out for the adaptor, and all the way back for drill bits. Might get a cordless 'driver, will save some aggro.

I found I had too many hand-tools - half a dozen trowels and hand forks, sorted out a couple of each and gave the rest to a charity shop.

@ Thanks Karen. I'll get a bigger bag next time, and one that does'nt set so fast - I had the idea of varying "mod roc" - plaster-impregnated bandage, just dip it and wrap round hte object and let it set. I had the idea of seeing if this would work with concrete - won some out-of-date bandages on eBay, just need to find something to wrap it round - which will involve a wire or papier-mache skeleton.

could also have a go at making individual plant pots, rther than troughs - easier to move around.

@ Stroller - for a very first go, they're passable - I could indeed use them for decoration; maybe I could paint them as well - lol at least to get them back to concrete colour!

I did think of using sand as the "mould" - at least I should be more able to see where the impressions are! but the concrete would still stick a bit. still, it might not be so dark a finish!

14 Jun, 2014

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