We received an interesting inquiry from a customer regarding the bituminous primer Grundbit from the manufacturer Bornit. The material is used as an adhesion promoter for the preparation of the substrate prior to the laying of welded strips or as a primer for subsequent bituminous coatings. Since spraying is usually carried out on large areas where hundreds of square meters often have to be covered in one go, the use of an airless pump is considerably more economical than application by roller. But this raises a few questions that we answer in this blog post.

Spray a bituminous product with an airless

Spray a bituminous product with an airless

Question from our client:


We would like to spray a bituminous primer for a construction site. Therefore we would like to order the appropriate nozzle from you. And we would like to know if this is possible with our machines and if they will still be usable for plaster and dispersion paint. We have the following machines available:

Graco Mark X ProContractor
Graco Mark VII Max / ProContractor

Bituminous primer: Grundbit without solvent

Which nozzle do you recommend? What settings?

Which airless pump is suitable for spraying Bornit bitumen?

This bituminous primer is not very viscous and can therefore already be applied with a relatively small airless pump like the Graco ST Max II 595. However, since the application is usually done over a very large area, it may make sense to use a more powerful spray device. This allows the use of larger nozzles and thus significantly increases the yield per square meter.

In addition, longer hoses can be connected to more powerful sprayers, allowing the airless device to be held in one position and the entire roof to be coated without having to move and rearrange the workstation, thus saving time. Another argument in favor of a more efficient airless device is the use of the same device for the final coat of bitumen. In this case, the material used is usually thicker, so more powerful machines are required for spraying bitumen.

The most popular models for spraying bitumen are the Wagner HC 950 E, the Graco Dutymax GH300 or, among the most powerful airless machines in this segment, the Graco GH 833.

Graco-Dutymax-GH-300-DI Quelle buse utiliser pour projeter un produit bitumeux?

Graco Dutymax GH 300 DI

The customer has at his disposal the Graco Mark VII and Graco Mark X sprayers. These are high performance piston pumps that are perfectly suited for use on large surfaces.

What nozzle should be used to spray this Bornit bitumen?

Bornit bituminous primer can be used with a 523 size nozzle for small areas. If you have a high performance airless device, then it is a good idea to use an 831 nozzle. This nozzle produces a wider spray pattern and significantly increases the surface output.

wagner tips

Useful accessories for bitumen spraying

In addition to the optimal nozzle size, there are other accessories that can make the job much easier and significantly increase the m² per hour output.

 No flat roof without a lance

It is much easier to work with an airless extension. A 90 cm long lance is well suited for coating floor surfaces or flat roofs. The advantage is that you don’t have to bend over and can coat comfortably while standing upright. In addition, overspray and paint waste are reduced, as the wand better maintains the optimal distance between the nozzle and the surface.

Always with a rotating joint

The lance must be used with a joint. This joint is mounted on the front of the lance and allows the user to obtain an optimal 90 degree angle between the nozzle and the surface.


Longer hoses for flat roofs

Most airless sprayers are delivered from the factory with 15 m long hoses. In many applications, this is sufficient. For bitumen coating, however, larger areas are usually involved, so it can be useful in this case to extend the hose and thus obtain a larger working area so that the airless device can be moved less often. We will be happy to advise you on the choice of the right hose extension for your application. In our online store, you will find an overview of all available hoses.

Direct suction from the drum for bitumen

If the bitumen is delivered in drums, it is recommended to process it directly from the drum. This avoids the time-consuming transfer from the drum to a smaller container. For this purpose, there are drum suction systems available which can be connected to the airless paint sprayer and allow the bitumen to be sucked directly from the drum.

20 Quelle buse utiliser pour projeter un produit bitumeux?

How to clean the airless pump after spraying a bituminous product?

Bornit offers a cleaner that is very suitable for the first cleaning. However, you will need to soap the machine and its accessories well to remove any remaining bitumen. Our video shows you in detail how to do this cleaning.


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Questions or queries ?

For any further questions or if you would like to get your hands on one of these products seen in this article, you can contact us on +49 (0) 30 220 15436, fill out our contact form or email us.

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