spray lacquer

[steamboat]

Hello all, I am new to the forum and fairly new to woodworking so have a lot to learn.
This is my first question:
I have been building a pair of loudspeakers for a while now, I have veneered them in figured cherry and plan to lacquer them to a high gloss finish, all going well so far. I am now on the lacquering part which I am doing by spraying; unfortunately this part isn’t going so well. I have sprayed about six coats, sanding in between coats, but I can’t seem to get the lacquer to go on thick enough so that it is wet, instead I get a finish that looks a little like it was put on by flicking a lacquer laden tooth brush over the veneer. I have adjusted and then re-adjusted the gun settings, what can it be???
The compressor is only a 1.5 hp, but I cant see why that would be the prob, the air presser is around 25-30psi I am holding the gun about 6-8 inches away from the work peace.
Please help.

Many thanks
Steve

 

[jasonB]

What type of lacquer are you using and how much are you thinning it by?

Are you using a regular spray gun, HLVP on a normal compressor or full HLVP?

Jason

 

[steamboat]

Hello Jason and thanks for getting back to me.
The spray gun is a Sealey gold series, not sure if this means much to you but as far as I know it is just a normal spray gun, the compressor is also just a normal 1.5hp compressor. The Lacquer is a Fiddes pre-cat cellulose based lacquer so no thinning needed.
The other points that I forgot to mention in the previous email is that the lacquer is going on in lines, most lacquer is being put down directly in front of the gun less towards the edge, I assume this is normal, also the room I am spraying in is filling with a fog of lacquer so I am wasting a lot of material.
Hope this helps

 

[jasonB]

Spraying is not really my thing but here are a few things to think about

Have you applied a basecoat or sealer coat

You should be spraying at 45-60psi

Is your small compressor upto the job as the Sealey gun needs 6-11cfm (thats free air delivery) which is higher than the cfm most compressor makers state

Pre-cat can be thinned if required by upto about 10%.

You say the spray is in a line, have you got it set to fan or is the spray width set to narrow.

Jason

 

[BradNaylor]

The compressor is only a 1.5 hp, but I cant see why that would be the prob, the air presser is around 25-30psi

I think that this is where your problem lies. You need to be spraying at around 50 psi to get good atomisation. I also suspect that your compressor is simply not capable of supplying enough air.

Dan

 

[steamboat]

Thanks all. After you advice I tried uping the psi and it is now working a treat, unfortunately, as was mentioned, the compressor cant keep up with the spraying, also I am still surrounded in a fog of lacquer but I suppose that is the disadvantage of spraying. All is needed now is better technique.
Thanks again

 

[BradNaylor]

Thanks all. After you advice I tried uping the psi and it is now working a treat, unfortunately, as was mentioned, the compressor cant keep up with the spraying, also I am still surrounded in a fog of lacquer but I suppose that is the disadvantage of spraying. All is needed now is better technique.
Thanks again

All that's needed now is a spray booth! Or go outside. A cheap gazebo in the back garden is a good idea for spraying under. If you live in a flat, rig out the balcony! :lol:

Seriously, all that overspray is bad both for you and for the quality of your finish.

Have you tried water-based lacquer?

Dan

 

[steamboat]

Iv got a garage with two openings which I usually get a good through draft through, I also wear a respirator with a gas vapour filter, which seems to work well. I have inquired about the water based lacquers but fiddes, the most local suppliers, said that it isn’t as durable as the cellulose based product. Any thoughts? :shock: :?:

 

[BradNaylor]

I've been playing around with a new water based lacquer developed by Morrells Woodfinishes. Initial results indicate that it is as durable as an AC lacquer. Just as importantly, it sprays as easily.

In five years time all lacquers will be water based.

Dan

 

[steamboat]

Hello all I seam to have struck a problem: after spraying around six coats of lacquer on my peace of work one side has started to delaminate in places, I assume this is because the first layer didn’t go down wet. Should I peal everything off and start again or is here a way of making good?
Thanks for your help :roll:

 

[Sgian Dubh]

after spraying around six coats of lacquer on my peace of work one side has started to delaminate in places, I assume this is because the first layer didn’t go down wet.

It may be a strip and respray job. If you're using pre-cat there are limits on the dry film thickness-- a maximum of about 5 mils is recommended by most manufacturers. This is achieved with a maximum of three coats of lacquer each applied at about 5- 6 mils wet.

Pre-cats, assuming it is a pre-cat you're spraying, will fail exactly as you describe if the coating falls outwith the manufacturer's thickness specs. It's a hard, brittle finish that cannot build up thickly as shrinkage of the upper portion of the polish pulls the stuff near the wood up. The other failure you'll see if the coating is too thick is what's known as cracking, usually visible as irregular lines running across the grain. Slainte..