QUESTIONS ABOUT CASTING IN CONCRETE

CAN YOU USE THE MOULDS MANY TIMES?
Absolutely – they are manufactured from flexible, tough plastic. The majority are quite easy to remove and won't break. Removing others requires a little more patience and some useful tips. Read the description that accompanies each mould.

HOW CAN THE SURFACE OF THE CONCRETE BE SO GLOSSY?
It depends on the moulds. Glossy moulds quite simply give glossy surfaces. When the mould is old and worn it becomes matte, but still as smooth.

HOW DO YOU GET RID OF ALL OF THE AIR BUBBLES?
Lay a millimetre thick layer first – pat and rub away the air bubbles. It’s important to be careful with the first layer! Lift up and look through the transparent mould – remove the bubbles you can see and check again.

HOW DO I MAKE THE CONCRETE AS WHITE AS YOURS?
Different makes vary considerably in terms of shade. It depends on where the cement and sand come from. I use Finja concrete which is a lighter brand than most.

WHICH OBJECTS SHOULD BE REINFORCED?
Those that are thin in relation to how big they are, such as worktops. Paving slabs have to be 5 cm thick for you to be able to walk on them to avoid reinforcement.

CAN YOU SEAL CONCRETE POTS?
Making a pot as watertight as a vase is to a large extent impossible. I quite simply choose to accept that concrete is a porous material. Put pads under pots indoors and choose plants that need only a little water.

I WANT MY CONCRETE TABLE TO BE AS TOUGH AS GLASS!
Unfortunately no such treatments are possible. A completely watertight surface treatment is not recommended on porous materials. There is a high risk that the moisture will seep in under a watertight surface treatment and make it ugly. Professionals first apply a sealer that sinks in and binds the lime and then a surface finish that repels liquids and grease.

SHOULD ALL OBJECTS BE TREATED?
I always treat worktops – but only certain other objects – to avoid stains from grease, food, coffee or wine. It can be sensible to protect trivets and candlesticks from food stains and candle wax. The same applies to a bowl that will contain fruit. Apply Betongvax, which doesn’t go yellow and which gives a satin finish – or Steinfix for a shinier, slightly more yellow finish.

ARE THERE RELEASE AGENTS OTHER THAN NORMAL COOKING OIL?
Air bubbles stick readily to greasy oil. Non­stick spray reduces the risk because it isn’t as greasy. Non-stick spray is available in larger supermarkets. Release agents used by the concrete industry are hard to get hold of and leave a white film on coloured concrete.

CARPET TAPE TO ATTACH DECORATION WITH
Carpet tape should have a woven structure in order to be strong. Check in your local shop whether the tape seems to be sufficiently strong and sticky.

REMOVE THE CARPET TAPE
Remove it with your fingers/nails, dry. You can also use a “tape ball” like chewing gum and dab to remove the residues. Wash the mould and remove the final residues with a scouring pad, washing-up liquid and hot water. If necessary, use a little methylated spirit to remove the final sticky residues. If this still isn’t sufficient, use a little acetone on a cloth.

WHY IT MIGHT NOT WORK...

MY RESULTS AREN’T AS GLOSSY EVEN THOUGH I'M USING YOUR MOULDS
1. The concrete may have dried too quickly. ALWAYS lay plastic over the mould and never allow it to dry in the sun.
2. Did you leave the concrete to dry for two days in the mould? Otherwise the glossy surface isn’t able to harden fully.
3. Poor concrete quality. The cheapest concrete is often not as good and contains more stone and less cement.
4. Old, poor quality concrete. Concrete is perishable and keeps for around a year if stored in dry conditions. See the date on the sack.
5. The glossy moulds gradually become worn and matte. Old forms become matte – but still just as smooth.

I CAN’T GET RID OF ALL OF THE BUBBLES!
1. Too much oil in the mould means that the bubbles stick.
2. Too much water can generate more bubbles.
3. Too little water means that the concrete doesn't run out easily.
4. Don’t be in too much of a hurry when you are mixing. Mix for a long time and leave to stand. Look carefully at the concrete for air bubbles and make sure it has stopped “crackling” when you start to fill the mould.

WHY IS IT SO HARD TO REMOVE THE MOULD?
1. It’s the vacuum in the mould.
2. No release agent.
3. The concrete has dried out for longer than 2 days.
4. The mould is full to the brim. Always leave a few millimetres so that the object can “fall” down when you turn the mould upside down.
5. A lot of decoration using double-sided tape makes it more difficult to remove.

HOW CAN I REMOVE IT?
1. Run warm water over the plastic side of the mould. The plastic will expand, the vacuum will release and the double-sided tape will soften. Take it easy and be patient.
2. Some people prefer to slit open troublesome moulds at the edges. Slit moulds can easily be taped together with silver tape before the next casting. This can include the Heart birdbath and Hemisphere birdbath.

WHY DO THE VACUUM FORMED CASTING MOULDS HAVE SMALL DOTS?
These small dots are suction holes which are necessary when vacuum forming. There are suction holes on ALL of the moulds which are not completely smooth – so the plastic can be sucked down and follow the pattern. The more detailed the pattern, the more suction holes there are. The dots are barely visible on the concrete object – as you can see on all of the images in this book.

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