Repel spots in water based lacquer?

[ian]

Spoke too soon, the repel spots came back with a vengeance on the second coat and then even more on the third coat.

This is a consistent pattern now. The day's first coat is always relatively even, with repel spots appearing with greater frequency with every coat I apply. Is this consistent with silicone contamination, or oil?

Edit: A thought just occured to me - I used baking paper to protect the iron as it went over the veneer as per its instructions. Could this cause any problems?

what you describe sounds a lot like oil contamination, starting with a clean gun, the more you spray the worse it gets.
Everything I've heard about silicon contamination, says that it starts off bad and stays that as bad as you spray extra coats.

my suggestion is
replace the water filter at the compressor
clean the air hose
install an oil trap filter immediately before gun (or install a new filter membrane in your existing filter)
run new air hose between the final oil filter and the gun

see what happens when you
1) spray on your test board and
2) spray onto a board that has only been sanded -- i.e. no veneer, no iron, no stain, no filler, etc -- if you get spots, the problem is definitely related to gun, the material and the air supply


at this point it might be worth while revisiting one of your other posts ...

So I spent a significant amount of money on a set of speaker kits. I got a little bit excited.

Got some oak veneer, an air compressor, gravity fed spray gun, moisture trap, steel wool, pumice, built myself a spray booth, some Haymes Aqualac, only to find out that nobody seems to recommend spraying my finish of choice - water based Acrylic Lacquer.

I've checked all the usual brands - feast Watson, Wattyl, Cabots, even Haymes. None of them specify spray gun as a possible application method on their WB acrylic lacquer tins. Asking a shop assistant got me basically "it's because of the way it goes on, it's just better with a brush." which doesn't really help.

Can anyone please shed some light on this? I've been going back and forth between varnish, 2 packs, polyurethanes and lacquers for weeks! The sheer lack of consensus on which terms mean what is bewildering.

Thanks in advance!

ps: I've been working with wood as a light hobby for about 14 years so you don't have to start from scratch when explaining things.

given this, do you still get spots if you apply the finish with a brush ?

[Kaisergrendel]

what you describe sounds a lot like oil contamination, starting with a clean gun, the more you spray the worse it gets.
Everything I've heard about silicon contamination, says that it starts off bad and stays that as bad as you spray extra coats.

I see!

my suggestion is
replace the water filter at the compressor
clean the air hose
install an oil trap filter immediately before gun (or install a new filter membrane in your existing filter)
run new air hose between the final oil filter and the gun

The thing that's puzzling me the most is the fact this whatever's contaminating the finish is actually *soluble* in my water based lacquer. I'm not getting fisheyes or adhesion problems even with the moderately heavy sanding I do with every coat to level out the craters. First thing I'm going to do is extract some of the filtered goop from the regulator and see if it mixes with the lacquer. If it doesn't, I can probably rule out oil contamination right there.

I can try replacing the hose but the regulator is a bit out of my means to replace at the moment. The filter under my gun never traps anything so I will have to source different one from elsewhere. Also the entire system is close to brand new with only about 2 months worth of sporadic use.

see what happens when you
1) spray on your test board and
2) spray onto a board that has only been sanded -- i.e. no veneer, no iron, no stain, no filler, etc -- if you get spots, the problem is definitely related to gun, the material and the air supply

I'm testing on some pine offcuts at the moment. I spray on the pine first, then spray on the test board, so it's the same batch of air/lacquer. The pine is extremely absorbent so it will be some days before I can reproduce the problem. (The repel spots aren't visible until there's a glossy coat on the surface)

at this point it might be worth while revisiting one of your other posts ... given this, do you still get spots if you apply the finish with a brush ?

After that post I gave up on the aforementioned Haymes aqualac as it was near impossible to get a good even coat by spraying. I'm now using Stewmac's Colortone WB Lacquer, which is meant to be sprayed, not brushed.

[tea lady]

After that post I gave up on the aforementioned Haymes aqualac as it was near impossible to get a good even coat by spraying. I'm now using Stewmac's Colortone WB Lacquer, which is meant to be sprayed, not brushed.

I was gonna suggest trying just applying it with a brush. Just as a test. We know it is meant to be sprayed, but if you eliminate the gun you can see if its actually in the lacquer.

[Kaisergrendel]

At first I thought it was a great idea until I noticed the way it goes onto the board. When sprayed, the lacquer is misted on, allowing the contaminant to stay in one spot and work its magic. When it's brushed, any potential surface contamination is smeared across the surface and possibly diluted till it's too weak to have any effect, particularly since the contaminant is actually soluble in the lacquer.

Wiped on two coats of lacquer no cratering. Regardless of the previous paragraph, I'm starting to believe it actually has to do with my air supply.

[tea lady]

At first I thought it was a great idea until I noticed the way it goes onto the board. When sprayed, the lacquer is misted on, allowing the contaminant to stay in one spot and work its magic. When it's brushed, any potential surface contamination is smeared across the surface and possibly diluted till it's too weak to have any effect, particularly since the contaminant is actually soluble in the lacquer.

Wiped on two coats of lacquer no cratering. Regardless of the previous paragraph, I'm starting to believe it actually has to do with my air supply.

The plot thickens. You'll be the water based lacquor expert after this.

[Kaisergrendel]

The plot thickens. You'll be the water based lacquor expert after this.

Ha, I imagine I will be!

[Kaisergrendel]

Okay, I'm on the lookout for new air filters. These are what I have at the moment (not exact model/brand but you get the point)

At the compressor:
http://www.tme.eu/katalog_pics/0/3/7...3g-3gk-qt3.jpg
Below the gun:
Water Separator - In Stock at www.ozintersales.com.au

I think I've come to the rude realization that, while these seemed expensive to me when I bought them, they're about cheapest, crappiest filters I can buy with money.

Took a look at this page:

Filters / Regulators / Gauges - In Stock at www.ozintersales.com.au

And ignoring the multi-hundred or thousand dollar filters, which I simply can't justify buying, (I'd rather switch to brushing) I'm looking at the next cheapest filter:

AMAXI Air Filter - In Stock at www.ozintersales.com.au

Anyone have any experience with this type of filter?

[The Bleeder]

Back again.

What type of compressor have you got. I've sprayed a lot of products and it comes back to the compressor, the medium, both of which you look for contamination and then finally the surface.

If the surface takes it (undiluted) by brush in thin (and I mean thin) coats then start looking at the other two.

Just because a compressor is new doesn't mean you won't have an oil contanimation issue. (This is what I think it may be).

The compressor I use is a twin cylinder ~130lpm FAD. Filters get changed reguarly. Used for a lot of things including nail guns and impact drivers. Separate hoses for these to the spray gun.

What hose are you running? This can also be a source ...just because it's new it may have already been contaminated.

Only suggestion I can make is find someone else that has a spray kit and see if they get the same result. If they don't then sorry but it's your system.

[Kaisergrendel]

Hey bleeder, I've tested on a piece of raw wood and reproduced the same problem, so definitely looking at oil contamination now. Checking the exit port of the regulator/filter shows that it definitely isn't filtering all the moisture out as I can see droplets of oil/water.

I've bought a new, different hose. Added a drip tap at compressor and moved the regulator/filter to near the end of the line.

My compressor is rated at 2.5hp 75lpm. No specification on the number of cylinders but it sounds like there's 2 of them to me. It only starts up every 2-3 coats because the sample board is so small.

Can you recommend a good affordable filter to me? preferably below $100 and not over $200.

One thing I noticed - I never thought much of it but I recently did an oil change because the compressor was started to sound noisier. I filled up the oil chamber till the oil was near the top of the target ring. The manual says to "fill the crank case until the oil reaches the red mark on the sigh glass." Since the "red mark" is a circle, it's a little ambiguous as to whether the oil level should be below, in the middle, or touching the top of the circle. Check the attached picture to see how it looks now.

I sprayed about 12 coats on my first sample board and 20 coats on my second sample board and *never* had this problem. I have a feeling my compressor is overloaded with oil and leaking it into the air.

General update: I found "prep wash" which the shop assistant told me is "the same thing" as prepsol. Indicated for removing silicone, wax and grease. Smells suspiciously like turpentine. Immediately after wiping down the board with it, twice, cratering has decreased, but not been eliminated. Not sure if this is just a coincidence. I stupidly used a heat gun to make sure the wash was completely evaporated before spraying lacquer, but the iron-on veneer came right back and bit me in the ass. I have steaks of delamination going on with grain protruding upwards from the substrate. The re-melting glue probably released water vapor and warped the veneer.

I sanded through an edge and two more corners this time while doing leveling. The cratering is probably making it far more difficult than it should be, but do you guys have any tips for levelling a finish without touching timber underneath?

[Kaisergrendel]

More questions:

1. Do you generally need to use brass/steel pipes in order for the drip taps to work? I'm using plastic ones at the moment.

2. How often do you need to exhaust the air tank? (I like the idea of leaving the air in for 1-2 days until the next time I need it, instead of starting from scratch.)

3. Is there any danger in fully opening the stop valve on the compressor to exhaust the air? (Explosive decompression?)

[The Bleeder]

Hi,

The oil level looks to be a bit on the high side. I keep mine at about the middle of the circle.

When using the compressor I tend to bleed the tank and empty any water that has accumulated every 2 days. If I'm not going to be using it after one session then I'll do it there and then.

Can you post a pic of you setup. All of my water and oil filters are at the compressor. I use different hoses for spraying to those that are used for other devices.

To empty the compressor I usually have some cleaing up to do so out with the air gun and once all the air is gone I'll open the valve and empty everything.

Now this might sound a bit on the bad side but....since I think you have overfilled it a full strip down and clean may have to happen.

[Kaisergrendel]

Hi,
Can you post a pic of you setup. All of my water and oil filters are at the compressor. I use different hoses for spraying to those that are used for other devices.

Yup, the pics are attached. First shot is the compressor with the hose hang straight up from the ceiling, directly outside the spray tent. Second is the drip tap, third is the hose coming back down and into a regulator. The coiled hose is the one I previously used. I'm in the process of reconfiguring it so it might seem a bit messy.

To empty the compressor I usually have some cleaing up to do so out with the air gun and once all the air is gone I'll open the valve and empty everything.

So you blow everything out through your spray gun? If so, that's what I do to, but I never have enough to clean so I find myself standing there for a few minutes holding the trigger down till it's fully depressurized.

Now this might sound a bit on the bad side but....since I think you have overfilled it a full strip down and clean may have to happen.

You mean take it apart and clean it out? Gosh, I may have to buy an entirely new one! I'll try draining some of the oil first and reconfiguring the air line before it comes to either of those options.

[The Bleeder]

Ok, from what I can see you need to get the water trap and primary oil filter at the outlet from the compressor. Then you can have a secondary where ever you like if you need it. Try looking in evilbay for an oil filter you might get lucky.

Yes I wash out the gun then spray it at everything outside, till the tank is basically empty (young son likes to take on the lizards with it).

Yes drain some of the oil and try to get it around the middle of the cricle (if it's a bit low in the circle that's not a prob). It depends on how much you have used it with it being overfilled, a primary and secondary oil filter might work untill most of the oil that has entered the tank etc.. has been disapated. (It's a bugger of job to strip and clean and rebuild them).

[Kaisergrendel]

Ok, from what I can see you need to get the water trap and primary oil filter at the outlet from the compressor. Then you can have a secondary where ever you like if you need it. Try looking in evilbay for an oil filter you might get lucky.

Thanks, I am looking for a filter to stick onto the compressor outlet, but I haven't been able to any besides the ones I can find from Bunnings or evilbay besides the ones I have. What kind of filters do you use?

Also, will using metal piping attract more condensation for the drip tap?

Yes I wash out the gun then spray it at everything outside, till the tank is basically empty (young son likes to take on the lizards with it).

I see, I guess I might stick to rubberbanding the air gun.

Yes drain some of the oil and try to get it around the middle of the cricle (if it's a bit low in the circle that's not a prob). It depends on how much you have used it with it being overfilled, a primary and secondary oil filter might work untill most of the oil that has entered the tank etc.. has been disapated. (It's a bugger of job to strip and clean and rebuild them).

I've used it about 10-15 cycles. (number of times it's started and stopped) Fingers crossed the tank is still reasonably clean. How hard would it be to disconnect the receiver tank and flush it with some kind of degreaser?

[ian]

How's the spray finishing going ??