Spraygun blocking - WB lacquer

[old_picker]

Started using Mirotone 8022 / 8060 precat waterbase sealer / topcoat combo early this year.
I found it quite excellent in most respects - sprays well, drys really nice and sands like a dream within hours. Holds its matt surface very well with wear. It is a great improvement in most respects on the stinky Mirotone high VOC 3022 I've been using for years.

However I am having problems with the guns blocking during a short 3 -4 minute spray job. Starts out spraying real nice and after a minute or two the flow will begin to slow. After a flush with water it will come back pretty quick. Surely I dont have to clear the gun every few minutes to keep the flow going?

The guns are gravity fed. The sealer gun is the standard size Star S770 with a 2mm tip the other [for topcoat] is a Star mini with a 1mm tip. The finish I'm using today was thinned and put in a jar about a months ago. The consistency that works for me is about about the same as unwipped cream. It comes off the small gun nice and smooth with lowish fluid and airflow. The sealer seems to gum up worse and you need to blast that through a bit harder.

Having used WB finishes in the early noughties I realise they are more high maintenance. Ive tried the usual suspects like the air bleed hole in the container, changing filters then a new filter and finally no filter. The gun was pulled down and fully cleaned last nite.

Any advice?

[Slave]

You could try filtering the finish as you put it into the gun

[Marty Schlosser]

If you're still having blocking problems with your sealer gun, it most certainly isn't due to the tip size, which is actually very large for most lacquers. I prefer a 1.3mm needle/nozzle size for lacquers.

I suspect, just as has already been suggested, that it's due to tip blockage due to unstrained finish making its was into the fluid path. You should ALWAYS strain finish as you pour it into your gun (or pressure pot). For the lacquer you cite, a medium size mesh strainer would be ideal.

[pictureman]

There will more solids in the satin/matt finish, so putting it through a strainer is the way to go.

[old_picker]

thanks for the advice
it was the finish causing the issue
it had gone kinda stringy after sitting
after putting it through a 100 mesh screen it was all good from there