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David
 
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Excellent advice for the OP, Mike. Much more focused response than some
of the others who prefer the "shotgun approach".

David

Mike Marlow wrote:

"MikeG" wrote in message
ews.com...

In article ,
says...

This is the first time I've tried to spray shellac. It was bullseye,


out of

the can, and I cut it with denatured alcohol. I sprayed it, and it


looked

ok at first, but as it dried, it seemed to pucker in spots and give me
orange peel. It's acting like I put it on too thick, but when i tried


to

lay it on thinner, it didn't seem to be atomizing correctly, and it went


on

a bit spotty. I put it on heavier to make it flow, but then it didn't


seem

to dry right. What did I do wrong? Not thin enough?



What you could be doing wrong could be not spraying the right viscosity
for the needle/nozzle combination, to much air pressure, to little air
pressure, too much air volume, too little air volume, incorrect fluid
flow, needle set too far out from the nozzle, needle set too far into
the nozzle, or any combination of the above.



This just about covers everything that *could* possibly be wrong, so it
really doesn't narrow things down for the OP. If there's orange peel then
the only reason for that is a first coat that is too dry followed by wetter
coats that the sprayer attempts to flow on. That's what creates the orange
peel - subsequent coats bridge the spotty coverage of a dry coat and create
the humps we call orange peel. You can't fill enough with additional coats
and it will always look worse after it dries than it does when it's wet.

Thinning the fluid should be per the manufacturer's spec. It's usually ok
to thin a bit more if the gun does not seem to spray it freely, but
generally starting with manufacturer's spec is a very safe starting point.
Air flow, pressure, etc. are easily adjusted by shooting at a scrap and
adjusting to get a good fan and a good coverage. You should easily be able
to flow enough to cause a run if you just hold the gun in one place. Spray
with a slow, steady pattern, just overlapping each pass. You should imagine
that you're stretching a thin film of that clear stuff that wives keep in
the kitchen cupboard and that *only* wives can properly stretch over a bowl
of leftovers, over your workpiece. One pass on an area. One pass. Not
two. Not a little touch up. One pass. End to end. Watch your flow as
you're laying it down. You'll see if it's going on too heavy. You want to
see it flow on. Let it tack up per the manufacturer's spec between coats.
No shortcuts here. Smoke a cigarette, load the woodstove, instruct the wife
in the art of changing car tires - whatever is necessary to distract you
while you give that coat the required flash time. Then you can put on
another coat.

Flash times and dry times are going to be affected by temperature and
humidity, as well as how thick the coats are. A good wet coat is thicker
than a dry coat, but not so thick that you should see protracted dry times.
It's not that you're trying to put it on thick, you're trying to put it on
wet. Keep that though in your mind. Remember the plastic wrap idea.

Most folks make the mistake of spraying too fast as they fear runs. Spray
too fast and you get dry coats which result in orange peel. It sands out,
so it's not the end of the world, but it is extra work.


It's unlikely that even a three pound cut of shellac would need thinning
but with the viscosity cup you will at least have an idea of where to
start. If you know you have the right viscosity and needle/nozzle
combination all you have to do is play with the air volume and fluid
flow and needle set.



Agreed the viscosity cup can be helpful, but the same can be achieved by
spraying at a scrap target and observing the fan. It's all a matter of what
makes you comfortable. I wouldn't want the extra step of the viscocity cup,
but others may well prefer to go that route.


The alternative is playing with all the factors in the rather large
number of combinations they present.In other words without at least some
fact based info you are just ****ing in the dark.



Not really. Again, you have the starting point defined by the manufacturer.
Thin to that point and start spraying on a scrap. Adjust the gun and tackle
the workpiece. There is no shooting in the dark, ****ing in the dark - (by
the way... if you're going to **** in the dark always make sure you know
where the electrical outlets are), it's just a simple matter of setting up
the gun. That's something you have to do anyway.