The right mix for sealer and enamel (water based) for spraying.

[gocat]

Hi there,

First of all, I have just started woodworking and have only just managed to cut a straight line on a table saw last week. I have just managed to assemble a simple cabinet. So far so good.

Now, finishing. It's a pain.

I have been spraying my cabinet for the last few days without success. Using the "Putty Spray Gun" from Bunnings with trial and error to get the right mix to spray (I don't have a viscosity cup).

Here's my equipment and material.
MDF board
British Paint - All in One - Sealer Primer undercoat (Water Based)
British Paint - H2O Enamel Full Gloss
Putty Spray Gun
Compressor 2.5HP (borrowed from a friend).

I'm sure I'm using everything wrong, but with what I have, I just want to know what will be my best possible outcome.
I guess I was painting the mdf like painting an internal wall. Sanding the undercoat it's like sanding an eraser.

Anyway, getting the right paint consistency for the spray gun is something I can't get right (thinning the paint with water).

Here's some of my settings
1. 150ml Sealer + 15ml water, 45 PSI, Hollow cone nozzle - Patchy Blob droplet
2. 200ml Sealer + 25ml water, 20 PSI, Full cone nozzle - Nothing comes out.
4. " , 45 PSI, Hollow cone nozzle - Paste (squeezing a tooth paste)
n. ... all fail...

Finally,
7. 200ml Sealer + 200ml water, 30PSI, Full cone nozzle
8. 200ml Paint + 200ml water, 30 PSI, Full cone nozzle

At 50% paint + 50% water, I get a milky paint, it sprays out ok. But the droplet are inconsistent. The spray distance is about 10~15 cm from the surface. There are large patchy and small droplets. I was expecting a mist like droplet.

Is this the expected outcome for this kind of paint?
or i had my mixing potion wrong?
or my settings are wrong?
or all above? :-)



kimc

[munruben]

Water based paints have always been problem to spray with an air compressor. Achieving the ideal atomisation of the material is to say the least, somewhat difficult. Low pressure and water based paints are not an ideal situation as far as I have found anyway. gravity feed guns are superior to the type you are using.
Switch to oil based paints and you should have no trouble, it will atomise and spray beautifully and give you a nice finish. Just play around with the mix until you get it right.
Not sure if the putty gun you are using is suitable for the work you are doing but I see no reason why it wouldn't be suitable.
When I was spraypainting and using water based paints, it was applied with an airless spray equipment and of course worked on a very high pressure to achieve the fine misty spray we need to achieve good results.
Other members on here may have some experience with the gun and material you are using.

[gocat]

Now I'm seeing the advantages and disadvantages of oil vs water based paint.

The mixing and spraying experience has a bit nerve wracking. The combine water and oil based paint are over $200. First things was, mix and hope for the best, then spray and hope for the best. I was kind of nervous, I was literally watching paint dry. On the 40 degrees day, that kind of speed up the process a little.

When the coat didn't turn out the way I wanted. I would sand it flat again and repeat 2 or 3 coat on the primer.

It was worst for the top coat. I thought buff-ing it (using car polish) would help bring some shine and flatten some of the bumps.
http://farm8.staticflickr.com/7154/6633508877_4b4fe0180c_z.jpg

That didn't help at all. Shown here a comparison of my (professionally done) 2-pack kitchen cabinet door. The water base enamel is just no match.
http://farm8.staticflickr.com/7172/6633512357_ecb1403a9c_z.jpg


So, I went to SuperCheap Auto to get 3M Quick Dry Enamel paint. No turning back at this point. I sprayed the front surface of all my panels. Again, even with the official mixing portion (4 part paint : 1 part thinner), it was a little too thick for my spray gun. Now, high gloss but still bumpy.

I wet sand them at 400 grit (that was the finest sand paper I have in hand). It's a mistake, it make it worst, it has lost all the gloss. I decided to apply the second coat. This time I'm going to flood the surface as much as I could while thinning out the paint a little more than the manufacturer's recommendation. Somewhere between 3 part paint : 1 part thinner.

This time is a little better.
http://farm8.staticflickr.com/7157/6633602277_b09f84d23a_z.jpg
The bumps were cause by the under laying primer. I've kind of given up on fixing that. But there is new problem - small dots. Looks like little grain of micro dots, I'm not sure how much you can see it in the photo.

Before the paint finish drying, I grab the smallest board and buff-ed it. To my surprised, it make it worst again. Those small dots were small air bubble trapped under the paint. The board now has popped pimples all over the surface.
Again, panicked and wet sand it at 400g to remove it.



I'll try one more attempt to repair the damage one of this 2 days.

[Geoff2005]

Hi
I have some things to add here for what its worth.

I embarked upon a program of painting doors in my house using Aquanamel. After achieving very average looking results with brushing/rolling I went down the spray route.

Renovate Forums (http://www.renovateforum.com/f207/painting-doors-can-you-get-good-job-acrylics-enamel-stays-white-77976/)

So far have achieved best results with Wagner airless spayer and 0.65 nozzle. But I suspend the door by its top/bottom so it is like a table and I spray the top, applying 300 - 400ml in under a minute. Results in a wet look surface, that would run in a vertical or inclined surface, then the sheen fades as the paint drys to result comparable a fair oil based roller finish. I use 10% water dilution with a few drops of "MorningFresh" detergent.per 2 litres. Dulux hot weather thinners improves the paint workability however I have found the resultant dry gloss appears to be lower and if you spray over a coat that has been thinned with DHWT then areas of oil/water type repulsion occur as the first coat sweats the DWHT which then doenst mix with a sprayed layer on top (it would if you aggitated with brush or something).

If I try to get a traditional type result from spraying Aquanamel then I cant, allways get an orange peel texture as the paint flashes off too quick and doesn't "melt" to a uniform surface.