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A
Z
Make models: metal etching
Current
2020
list Article list

Make models: metal etching

For this edition of Model Monday, we thought we would look at a specific process used within our work as modelmakers: metal etching.

What is metal etching?

Metal etching, or ‘photochemical machining’, is an amazing process that can be used to produce incredibly finely-detailed components that would be difficult, if not impossible, to produce by any other means. As well as model parts, etching can also produce items like delicate electronics, spacecraft components, jewellery and ultra-fine meshes.

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To produce a metal-etched part for a Make model, we draw it up in CAD and send it to a specialist firm, where they lay out the CAD data to make a pair of ‘phototools’, or transparencies, of the part. These tools are then used to apply a photo-resistant ink onto both sides of a thin metal sheet.

The metal then passes through a machine which sprays it with an acid solution. Where the print is applied, the ink resists the acid and preserves the metal. Where there is bare metal, the acid eats through it, leaving a crisp hole. By printing both sides, the etching can be controlled to create fully etched holes or half-etched details, like panel lines or brick and blockwork.

After cleaning and drying, the frames of parts are packed and sent to us, ready to be clipped out, painted or polished and, finally, applied to a model.

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We commonly use etching to make components like railings, balcony balustrades, window frames and complex patterned facades. Parts can be 2D, or designed as flat elements with fold lines, that are then bent to shape, glued together or attached to other model elements. A variety of metals can be etched, though we mostly use brass, stainless steel or nickel silver. Brass is generally used where a part will be painted, and stainless steel and nickel silver where we want the metal colour to be the final finish.

Metal-etched Make models

Our model of 5 Broadgate makes extensive use of stainless steel etching, to capture the finish of the real building’s distinctive facades. Etching allowed us to not only create a dazzling real metal quality, but also to express the panelled detail of the surface, along with the intricate roof vents. Another advantage of metals as a material is that they are totally light-tight, which is important with an internally lit model like this. With a laser-cut plastic model, we might have had to spray multiple layers of black paint to interior surfaces or apply light-blocking tape to seams to prevent light-bleed. With metal, this is just not a problem!

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5 Broadgate model
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With the concept model for GDH Nansha, the perspex-stacked core is clad with stainless steel etchings. The fine detail of the facade grid is perfectly captured and reflects adjacent detail beautifully. This model also features nickel silver canopy elements that add a subtle, pale golden hue to the model and complement the steel beautifully.

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The Luna project in Hong Kong features hundreds of perforated metal balconies, and we decided to use etching to capture this for the model. The concept stage models feature stainless steel strip with different sizes of etched circular patterns, hand-bent to shape and attached to perspex cores and floorplates.

When the project neared completion, we built a showcase 1:100 scale model of the design as built. We once again used etching to produce the balconies – in this case brass was used, as the model was to be full-colour, with painted detail. The balconies were drawn as a flat net, etched and then folded to their final shape before being glued into position.

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