The Content Of The Article:

With this type of mold, you can reproduce cheaply, and as many times as necessary, a decorative element for your home. All the necessary products are easily found in supermarkets and the initial investment is quickly amortized.

Text & Photos B. Petitfalaize

Practical advice

Remember to protect the floor with a large plastic sheet placed under a long table, whose horizontality has been controlled with a bubble level.
● The pouring of the resin and the application of the glass fabric are delicate moments. Perform these "blank" operations to break the sequence of gestures.
● Small mold defects can be easily corrected by using body builder or sandpaper.

The initial model can be polystyrene, polyurethane or even staff. Copies are made with casting plaster or, better still, dental plaster. More expensive, it is distinguished by a finesse of exceptional reproduction in the details. Moreover, its very good mechanical strength is recommended for the mass production of elements exposed to shocks, such as chair rails made here.

Supplies

For a chair of 200 x 8 cm, it is necessary to make a formwork in plywood of 15 mm thickness. For the actual mold, get two jars of polyester resin, one square meter of glass cloth, two flat brushes first prize and a pair of latex gloves. With the plywood and the pre-painted polyurethane molding 8 cm wide: the expenditure amounts to about 65, including 20 Euros for the molding.

Formwork

Plywood has the advantage of providing perfectly flat surfaces and perfectly straight edges that facilitate assembly by screwing the different parts of the mold. This consists of a bottom of 200 x 12 cm and two edges of a height corresponding to that of the item to be reproduced, plus 5 mm. Two drops of 12 x 4.5 cm close at each end. Assemble these elements with screws Ø 3.5 x 30 mm, spacing them 20 cm to fix the edges on the bottom.
● Stick the molding on the bottom, well centered. Then unscrew the edges and drops at each end for the application of a release agent. This product, an engine oil, is to be spread on the molding, the bottom and the drops of ends but not on the edges. You may be able to seal the edge of the molding with sanitary sealant, before reassembling the formwork.

Resin

In a clean, dry container, mix the contents of each resin jar with two-thirds of an accelerator vial. Hardening occurs after twenty-five minutes. It is therefore necessary to operate methodically and prepare the work carefully. In particular, by cutting in advance the glass fabric reinforcement strips (15 cm wide and 50 cm long).
● The use of resin requires certain precautions such as good ventilation of the premises where you work, wearing gloves and goggles.

Molding

Molding

A plaster bag of 40 kg (about 14.5 Euros) and a doll of tow (less than 5 euros) will allow you to make about fifteen moldings of 2 m long. If you opt for dental plaster, count about 32.5 euros the bag of 35 kg (Lambert, at Point P). The calculation is quick: for the same rendering, the molding technique is ten times more economical than single ornamentation!
● Strike the plaster in a trough by pouring 2 kg of powder onto 1.5 l of water (not the other way around!). Stir well, and pour the preparation into the previously oiled mold. Throw a bunch of lint into the cool plaster, vibrate the mold with a mallet to chase air bubbles. Unmould as soon as the plaster has set and allow the element to dry well. Start over again!

Assemble the formwork elements

Assemble the formwork elements

Drill pilot holes every 20 cm, then assemble the shuttering elements with Ø 3.5 x 30 mm screws. Placed face to face on the bottom, the edges are screwed from below.

Oil molding and background

Oil molding and background

The molding, well centered and fixed by two threads of wood glue, and the bottom receive an application of engine oil. Also put on the falls of ends but not on the edges.

Apply putty

Apply putty

Before reassembling the formwork, lay a thin bead of silicone sealant around the molding on the contact line with the bottom. Smooth with a piece of potato.

Apply tape

Apply tape

The tightness of the formwork is completed externally with wide-band adhesive tape straddling the junctions. This precaution will prevent the resin from escaping through the interstices.

Cut strips of glass cloth

Cut strips of glass cloth

In the glass fabric, cut some reinforcement strips about 15 x 50 cm. For convenience, put them near the mold, next to a cardboard dimensions slightly greater than them.

Prepare and pour the hardener resin mixture

Prepare and pour the hardener resin mixture

Prepare the resin and hardener mixture separately and pour it without precipitation into the mold to prevent the formation of air bubbles. Solidification takes about 30 minutes.

Apply the fabric and rub

Apply the fabric and rub

Impregnated with resin, the glass fabric becomes translucent. This is the moment to apply it on the profile of the molding. Slip from the middle to the edges of the formwork to chase air bubbles.

To apply the resin

To apply the resin

Apply the resin continuously to the projecting parts of the pattern until it has been transformed into a gel state. This is important for the success of the mold and the fidelity of the patterns reproduced.


Video Instruction: Mold Making And Resin Casting - How I Make Plastic Copies of My Toys