Scratch building is the process of building a scale model

Scale model

A scale model is a physical model, a representation or copy of an object that is larger or smaller than the actual size of the object, which seeks to maintain the relative proportions of the physical size of the original object. Very often the scale model is used as a guide to making the object in...

 "from scratch", ie. from raw materials, rather than building it from a commercial kit, kitbashing

Kitbashing

Kitbashing or model bashing is a practice whereby a new scale model is created by taking pieces out of commercial kits. These pieces may be added to a custom project or to another kit. For professional modelmakers, kitbashing is popular to create concept models for detailing movie special effects...

 or buying it pre-assembled.

Scratch building is easiest if original plans

Plans (drawings)

Plans are a set of drawings or two-dimensional diagrams used to describe a place or object, or to communicate building or fabrication instructions. Usually plans are drawn or printed on paper, but they can take the form of a digital file.- Overview :...

 of the subject exist; however, many models have been built from photograph

Photograph

A photograph is an image created by light falling on a light-sensitive surface, usually photographic film or an electronic imager such as a CCD or a CMOS chip. Most photographs are created using a camera, which uses a lens to focus the scene's visible wavelengths of light into a reproduction of...

s by measuring a known object in the photograph and extrapolating the rest of the dimensions. The necessary parts are then fashioned out of a suitable material, such as wood

Wood

Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...

, plastic

Plastic

A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

, plaster

Plaster

Plaster is a building material used for coating walls and ceilings. Plaster starts as a dry powder similar to mortar or cement and like those materials it is mixed with water to form a paste which liberates heat and then hardens. Unlike mortar and cement, plaster remains quite soft after setting,...

, clay

Clay

Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...

, metal

Metal

A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

, polymer clay

Polymer clay

Polymer clay is a sculptable material based on the polymer polyvinyl chloride . It usually contains no clay minerals, and is only called "clay" because its texture and working properties resemble those of mineral clay...

, or even paper

Paper

Paper is a thin material mainly used for writing upon, printing upon, drawing or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....

, and then assembled. Some purists consider a model not to be truly scratchbuilt unless all of the parts were made from raw materials. However most modellers would consider a model including commercial detail parts as scratchbuilt.

Motives

The reasons hobbyists scratchbuild may vary. Often a desired model is unavailable in kit form in the desired scale, or entirely non-existent. Sometimes the hobbyist may be dissatisfied with the accuracy or detail of kits that are available. Other times a hobbyist will opt to scratchbuild simply for the challenge. Less frequently a hobbyist will scratchbuild out of economy, as sometimes the raw materials cost less than a packaged commercial kit.

Techniques

Most hobbyists develop their skills by building kits, then progress to kitbashing

Kitbashing

Kitbashing or model bashing is a practice whereby a new scale model is created by taking pieces out of commercial kits. These pieces may be added to a custom project or to another kit. For professional modelmakers, kitbashing is popular to create concept models for detailing movie special effects...

, where various kits are combined to create a unique model before attempting to scratchbuild. Sometimes scratchbuilders utilize discarded parts of other models or toys, with or without modification, either in order to speed up the building process or to allow the process to continue in spite of certain parts being difficult to make. Some companies sell parts that are of little use to anyone but scratchbuilders.

Building Stock

Building stock, in whichever material, can be plain sheets, strips, bars, tubes, rods, or even structural shapes such as L or T girders. Stock can also be embossed or textured to replicate a certain prototype material (such as plastic sheet embossed with grooves to mimic a scale brick wall).

For example, to scratch-build a small board fence, the modeler could use plastic rod stock to form the vertical posts, then use plastic bar stock to form horizontal rails affixed to the posts, lay plastic strip stock vertically on the horizontal rails (perhaps 'distressed' with a wire brush to mimic wood grain, or by using thin strips of actual wood), trimming the top and bottoms of the strips to be even, adding details like nail holes (using a small pin), and then finishing and weathering

Weathering

Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...

(making a model look like it has been used via dust, dirt, stains, and wear).

Method

There are as many ways of scratch-building models as there are modelers, but generally the modeler obtains plans of a prototype, or designs his own, transfers these plans to paper or other material as patterns (much easier since the arrival of household computer printers and copiers), and uses these patterns to cut, trim and affix the stock together to form the model. Finishing work (such as sanding and polishing, painting, weathering, distressing by forming dents and rust, dust, etc.) is done to complete the model and (hopefully) bring it to a life-like state.