GREX TF-3 0.3mm Fan Spray Cap

Reviewed by Cookie Sewell

Summary

FirstLook

The laws of physics are one law most modelers try to break at their peril. One basic law of fluid motion is that an airbrush using a jet and a needle arrangement, no matter whether the most simple single action design or the most complex double action arrangement, will always spray paint in a conical pattern. For most of us, that is fine when we are dealing with a small area needing tight coverage. But for larger models needing either single colors or broader coverage it can cause problems such as paint drying before hitting the surface, build up and runs in some spots and uneven coverage.

This new items from GREX converts many of their popular airbrush series to now spray in a fan pattern for broader coverage. This is accomplished by using a specially designed head with two rotatable air horns to draw the paint off the needle in such a manner as to create the larger oval pattern shown in its directions. 

Installation is relatively simple. The handle is unscrewed and the needle removed or at least pulled back from the jet assembly and then the nozzle cap is unscrewed and removed. The new fan spray cap is screwed on in its place and then the needle is reinserted. 

Once the airbrush is reassembled, the pattern is set by loosening a locking nut and setting the air horns in the desired direction: horizontal relative to the air brush body to produce a vertical fan spray, and vertical to the body to produce a horizontal fan pattern. While this sounds contradictory, it is correct based on the physics of the air and fluid flow. 

The only adviso in the directions was that the airbrush should not have any fluids in it at the time of the switch, so care must be taken to ensure no paint is in the wrong place at the wrong time to cause backups or other problems when using the new cap. 

GREX indicates that you will need higher pressure (air flow) settings to operate the airbrush with this cap and does give a handy chart to show what it will take. Note that the caps are also offered in 0.5mm and 0.7mm sizes but they also require much higher pressure; their representative, Bryant Dunbar, indicated that their compressor worked best with the 0.3mm size needles and would be more difficult to drive a 0.5mm size and probably not get enough out for the 0.7mm one. Mine produces a maximum of about 32 psi (2.15 bar) with a Genesis XG hooked up so think he is correct in his advice. 

In summary, this is a handy accessory and one that may make large area coverage much easier and smoother. 

Cookie Sewell