How can I use stretched sprue in modelling?

Stretched sprue is a modelling technique frequently used by modellers that can be utilised to create a number of additional parts and effects for models. On most injection moulded plastic kits the parts will be provided on a series of plastic attachments called sprues. In most cases, these become redundant after the kit has been assembled and are then frequently thrown away. However, it is useful to hang on to a small selection of these sprues as they may be of further use. It is possible to take a section of sprue and stretch it over a small naked flame such as a candle or cigarette lighter. Simply take the sprue section and taking care to keep it above the flame gently rotate the sprue so all its surfaces are equally exposed to the heat. After a few seconds, you will start to notice a sag in the sprue where the heat has started to weaken its internal structure. Simply remove it from the heat and pull both ends of the sprue apart in order to create a stretched part with a much smaller cross-section. Inevitably this may take a few trial attempts to get right, so it is a good idea to have a selection of sprue sections to practice with.

The key is to pull with a consistent level of force. A quick pull will result in a very thin cross-section of sprue, conversely, a slower pull will result in a thicker section. Once pulled to the desired consistency leave the sprue to cool on a surface and then simply cut it to the required length. With practice, stretched sprue can be used to yield a number of useful items for a wide range of models. These include whip aerials for vehicles and ships, biplane rigging struts and HF antennas or other types of rigging for ships. For those looking to display a model with an exposed engine then stretched sprue can also be utilised as spark plug connectors or fuel lines as it has sufficient flexibility to take a significant bend. Also if more drastic curves are required then after removing it from the heat source the sprue can be wound around an object with a circular cross-section such as a small paintbrush to induce a stronger curve. Also, it can be used to fill unsightly seams or gaps where the use of putty or other filling mediums may not be practical.

Although a very useful technique care should be exercised when stretching sprue over a heat source as any vapours released are toxic and will be harmful if inhaled. For this reason, some modellers will choose to use this technique either outside or in a well-ventilated space. It is also a good idea to consult the instructions for the model kit from which the sprues have come as not all sprues are suitable for this process and some manufacturers are careful to offer this advice in the safety notes on the instruction sheet.