I am having difficulty maintaining a stable spray pattern when spraying Crystalac acrylic laquer with a Wagner 2600 HVLP sprayer. I get plenty of airflow, but the fluid flow is intermittent. It acts like it is plugged, but the gun is clean and the fluid was filtered before use. I am now suspecting one of two problems. Either the viscosity is too high or the seal between the cup and gun is leaking.
I am using Crystalac right out of the can. They say not to thin with solvent. (It is water based) Is there a way to reduce viscosity without harming the properties of the resulting finish?
If the seal is leaking, that could cause the siphoning to be inadequate, causing the intermittent flow. Does this sound plausible? The gun has been unused for at least two years, so the seal could have taken a permanent set. There is some appearance to this effect.
To those of you with experience with this sprayer, does this line of reasoning make sense? Are there other potential causes?
Thanks for your help,
Tom.
Replies
On a siphon cup gun like the 2600, the seal between cup and gun does not matter. There has to be a vent hole in the top anyway.
Do you have the vent hole positioned toward the back of the gun, such that paint in the cup cannot block it when you tilt it forward to spray on a horizontal surface or sideways to catch odd angles?
Crystalac may be too thick for your gun to siphon well. When they say do not thin, They are concerned that additional water will cause sagging and may reduce pH value too low for stability.
I reduce waterborne products with a 10:1 mix of isopropanol or ethanol [rubbing alcohol, to reduce viscosity] and household ammonia [to maintain high pH that emulsion resins need]. Lowered viscosity makes for good siphoning and atomization with HVLP, and the heat of the air evaporates most of the alcohol off before it hits the substrate, so anti-sagging properties are not ruined.
BruceT
Edited 9/9/2007 11:55 pm ET by BruceT999
BruceT,Thanks for the input. The gun does have a vent with a back check valve. It is located in the back half of the gun, so it doesn't get covered with fluid when the gun is tipped forward. Another thought: the back check valve could be plugged. I will check that out this morning.After my post, I noticed that a viscosity reducer is sold by the same outfit that supplied the Crystalac. I was going to try that product, but with your information, I will first try the alcohol/ammonia blend.Best regards, Tom.
Alcohol/ammonia is cheaper, but "official" reducer may be safer in case of warranty claim.
BruceT
BruceT,I found that the back check valve was indeed clogged. On this gun, the cup is pressurized with air that is delivered through this back check valve into the cup. With it partially clogged, the pressure in the cup was low and the flow of material to the nozzle became intermittent. Because of this, I think the seal between the gun and cup is also important to maintain pressure in the cup. So, I was able to find replacement parts locally this morning. I installed them and tested the gun with water. It worked perfectly. I still think I will thin the acrylic lacquer a little to improve atomization.Thanks again for your help. I feel like I finally understand this gun pretty well.Tom.
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