color break
k2 red telephone box
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How I made my K2 Telephone Box
Author: Les Kenny; Editor: Maree Anderson


Step 1.4. continued

Hypertufa - the curing process
This is probably the most crucial segment of the hypertufa application.

Curing time - The longer hypertufa is left to cure (set) the better. I kept the hypertufa moist at all times during the curing process, which went on for ten days. It was easy to contain the moisture with a polythene (plastic) sheet covering the hypertufa.

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keeping the hypertufa moist Once the hypertufa had been poured, we waited about four hours until the mix had just firmed enough to allow a sheet of polythene (plastic) to cover it without damaging the mix.

Through that initial time we kept the hypertufa moist, mist spraying it a couple of times.

a cover over the hypertufa Why cover it with polythene?
As mentioned before, hypertufa must be kept moist during the curing process.

One of the main culprits that causes the hypertufa to dry out during the curing period is evaporation.
Obviously this is even more of a problem in hotter temperatures.

Enter the polythene cover -
By covering the hypertufa with polythene the moisture in the mix can't evaporate because it can't get out.
Therefore, all the drying out is from a chemical reaction that happens between the cement and the water called 'hydration'.

I kept the hypertufa covered for a total of ten days. (Note that on day 4 I added a skim coat of slurry - see Step 1.5.).
Once a day I lifted the cover for a look-see. Everything was always still moist but I would give it another hose anyway ( a good old saturation) while the cover was off. Then I would put the cover back on again.

Sometimes in the heat of the day, the cover got pretty hot. But that didn't seem to matter.