To coat large surfaces without resorting to an Airless sprayer or a lengthy, tedious manual application, some professionals opt for a screw-pump machine. This device makes it possible to cover extensive areas in a short time. Well known to painters for many years, the screw pump is praised for its robustness and efficiency. Less precise than Airless and more difficult to handle, it is nevertheless appreciated for covering large volumes without losing time on cleaning or other auxiliary steps. However, applying compound with a screw pump is a technique that must be mastered if you want to achieve at least a tidy result.
Equipment for using a screw pump
Also called a “plaster pump,” the screw pump has a reservoir in which the compound is mixed to the desired consistency and then transported to a spray nozzle via a screw mechanism. The nozzle then projects the compound onto the surface, giving the professional a considerable saving of time and effort. To apply compound with a screw pump, the right equipment must be prepared. The key element is obviously the screw-pump machine itself; various models exist, more or less large and more or less recent, and it is wise to choose the one best suited to the project.
Another essential element is the compound. Several options are available, and some products are more suitable for screw-pump application than others, so be sure to choose a compatible product and follow the manufacturer’s preparation recommendations.
Various accessories and tools complete the kit: for example, jointing knives and smoothing blades useful at the finishing stage, spray nozzles that fit the screw pump, and protective equipment for the operator (safety goggles, gloves, masks, etc.).
Which technique should you use?
A successful screw-pump application follows a precise procedure, similar in broad terms to Airless spraying. The first essential step is preparing the substrate. To avoid imperfections and irregularities that would make the final finish look sloppy, it is vital to check that the surface is clean and dry before coating. If not, it must be dusted, washed and sometimes even sanded and filled beforehand.
Using a screw pump is not always convenient: the machine is heavy and difficult to move. Yet it is crucial to spray evenly, maintaining constant pressure and distance. Regular, steady movements are essential for uniform application.
Tips and pitfalls to avoid by using screx pump
For safety and while learning to handle the screw pump, it is advisable to start with the machine set to its lowest speed, depending on the type of compound and the surface to be treated, then increase gradually until the desired spray rate is achieved. Be aware of the machine’s manoeuvrability: although not easy to move on a worksite, it must follow the operator’s movements throughout the operation if you want a uniform, neat finish. This implies moving the device at a steady pace. Otherwise the compound will be distributed unevenly, which will be obvious once the job is done.
Finally, watch out for cleaning and maintenance. Unlike other devices such as Airless sprayers and bazookas, the screw pump is more robust and can continue to operate several times without necessarily being thoroughly cleaned between each application. That does not mean cleaning is optional. Over time the risk of blockages increases and malfunctions may occur.