In the preparation of a substrate before painting, the step of bonding joint tapes is both crucial and technical. Joint tapes are strips used to cover the seams between plasterboard or gypsum boards. They prevent the formation of cracks on finished surfaces and provide a sufficiently solid base for applying compound.
To maximise the quality of the finish while limiting the time spent on site, mechanisation can prove particularly effective. Several tools allow you to stick joint tapes and thus obtain a smooth, uniform surface ready for paint. Among them is the banjo.
What is a banjo?
Here, “banjo” does not refer to the small folk instrument we all know, but rather to a professional tool used to stick joint tapes faster and more evenly than by hand. Specially designed for this task, the banjo resembles a large version of a correction tape dispenser. It consists of a reservoir for the compound and a toothed wheel that distributes the compound evenly over the joint tape. Several models of various sizes are available.
What technique should you use to stick joint tapes with a banjo?
To apply coating to joint tapes using a banjo, you must first choose the right banjo model and the appropriate compound. It is generally recommended to opt for a ready-mixed compound. It then needs to be prepared and placed in the reservoir provided for this purpose.
Depending on the compound chosen and the manufacturer’s recommendations, it may be necessary to dilute it to make it flow more easily. A compound that is too thick can cause resistance when leaving the banjo; the risk is that the professional will have to force the tape, which can eventually break. The required dilution depends on the type and brand of compound. Professionals accustomed to working with a banjo generally judge the dilution by eye.
Tips for using the banjo
Bonding joint tapes with a banjo is not a particularly complex method. Suitable for both small and large surfaces, novices can certainly use a banjo to stick joint tapes. However, several pitfalls should be avoided to achieve a flawless finish.
Apply the right amount of compound.
Too much compound in a single pass can later cause cracks, blisters and uneven drying. It is better to apply a thin coat, let it dry for the necessary time and then apply a second coat if needed.
Respect drying times.
Drying time is also essential for quality work. Several parameters can influence how long drying takes, such as the humidity level or the ambient temperature. In summer the drying time will be much shorter than in winter. When in doubt, and to be safe, it is advisable to follow the manufacturer’s recommendations to the letter.
Know the banjo’s capacity.
A banjo reservoir generally holds enough compound to run four to five strips of 2.50 metres, which allows you to finish a room the size of a bedroom on average. To cover larger areas, you can use a pump connected to the compound bucket to draw the product and refill the banjo reservoir more quickly.
Modern banjos, such as the semi-automatic models, allow you to apply an even coat of joint compound and tape simultaneously over flat seams; they include features like flow gates with integrated tape cutters and adjustable compound flow. These design features save time, provide professional results and make the tool easy to master.