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patriot 08-06-2015 08:48 PM

Dumb, dumb, dumb, ...
I'm going to expose my stupidity, but hope this will help someone when they have a similar problem.

It's about my trusty gravity-feed spray gun. It just began pulsating - spray, no spray, spray no-spray etc etc etc .... This was driving me nuts. It was PERFECTLY clean. I could see through every orfice in the air nozzle, the fluid nozzle and the needle assembly was spotless. I could also see through the opening that the fluid passes through. It WAS CLEAN!! So what the heck was the problem?

The air pressure was set correctly. So what was the problem???

I have been using it to spray on water-based stain and shellac of the 1-lb variety. Both have the consistency of water. Nothing thick like latex paint. It worked fine about a month or so ago, but not now.

I used acetone to clean it after spraying stain and alcohol after spraying shellac. The acetone removed all of the brown residue of the stain so I know that worked.

The filter was a bit brown but I would always run either water or alcohol through it when done. But this made no difference at all. It continued to sputter.

Then today a little voice said, "Yo bozo, remove the filter and try it." I did and the pulsating was gone. I grabbed the filter and tried to blow through it and I could not. "But, but ..", I said, "It's nearly clear!" Yeah, well, in this case that meant NADA NOTHING. The filter was plugged even though it appeared to be clear.

So the moral of this story is just because the filter 'looks' clean or clear does not mean that it really is. It could be that the shellac caused this, but because I always ran alcohol through it after using it, I am not sure that shellac was the culprit in this case. Could be that filters just get plugged up and you have to replace them every once in a while. I am no expert so I am not certain of this.

I hope this helps someone.


patriot 08-06-2015 08:53 PM

Re: Dumb, dumb, dumb, ...
I just found these filters at O'Reilly's Auto - five for $17.

I think I'll just leave out this little filter and use a paint filter instead. It would seem that this would be cheaper and just as effective. Since I clean this spray gun very well after each use, I see no reason to purchase this expensive filter.

patriot 08-08-2015 08:05 PM

Re: Dumb, dumb, dumb, ...
1 Attachment(s)
Thought I would add a photo of the filter.

As I noted above I removed the filter from the spray gun and had no problems. That said, I am wondering what the shape of the filter has to do with how the gun performs?? The plastic nib fits downstream in the gun, but what purpose does the plastic nib serve?

Since the filter is no longer useful as a filter, I may remove the mesh and re-install the filter body and see if that makes any difference in how it sprays the shellac. It probably will not make a bit of difference.

Anyone have any thoughts on this??


PaulG 08-08-2015 09:25 PM

Re: Dumb, dumb, dumb, ...
Unfortunately I'm of no help, the most spraying I've done is with cans, airless and AAA, played around a little with the new Apollo, and none of it shellac. I've fought filter clogs enough to know there's nothing dumb about what happened, just another one of those life lessons learned through trial and error. Thanks for sharing your experiences.

RWeber 08-09-2015 03:54 PM

Re: Dumb, dumb, dumb, ...
That is a tiny filter. It would not take much at all to stop it up.
Shellac, especially, as sticky as it is, you would not necessarily be able to see.
At any rate, the role of the filter really is just to keep out chunks. There are a lot of spraying applications where filters are routinely removed, though clear topcoats probably is low on that list.
Examples - Think of a really big airless used to spray texture (drywall). Those pumps come with a rockbreaker on the end and an inline filter the size of a pop can. With mud, you leave the rockbreaker on and take the filters out.
If your gun (whatever gun that may be) has a filter as a part of the gun, and that filter is too fine for the material you are spraying, you can remove it, and simply filter all of the material through a fine mesh cone before it enters the spray setup. I rather prefer this. Periodically I spray this exotic post cat, expensive, fickle, urethane, and I have a pot dedicated for just that. New mix tub, new pot liner, every time. No filters in the lines.
For regular precat (gasp) I don't filter it at all. From the bucket into the pot. I've never had chunks in it.
For a paint, I'd think that a little foolish tho. Those just naturally have little bits of unground material in them. They'll jam a tip up readily.

patriot 08-09-2015 05:39 PM

Re: Dumb, dumb, dumb, ...
2 Attachment(s)

Thanks for info.

My spray gun was purchased solely for spraying shellac. At the time of purchase I was trying to fill walnut grain to speed up a french polishing project I was working on at the time. The gun was not very expensive as I recall, but it worked exceedingly well for my purpose or so I thought. (I am going to go into french polishing in this tread.)

At any rate, it is always my habit to clean the gun after use by running alcohol (in this case) to clean the gun. As noted above ( I think!) I also used it to spray a water-based stain/dye and the residue from this is soluable with acetone.

Because of this I would have thought that this would be sufficient to clean the filter. I also disassemble the gun and clean it piece by piece. The fact of the matter is that probably over time the filter was bound to clog no matter how well I cleaned it.

I have learned my spray gun lesson and now am good to go.

Thanks again for your comments.

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