Spraying Hard Shellac

[benldwyer]

Hi All,
At risk of raising the wrath of members, I am posting a query about spraying hard shellac. I have looked high and low for info re. this and have found a lot of people saying they spray it but not a lot of detail, and I'm new to spraying.
I'm have a basic stew mac gun (0.8 mm tip) as a starting piece and appropriate compressor, I've set up a little pop up camping tent as a booth to prevent dust etc.
I have sprayed about 5 coats of Shines hard shellac but continue to get craters in the finish, and while I continue to try to make adjustments to my methodology I thought Id ask here to avoid wasting too much more product... I have read about fish eyes, craters, bubbles etc. but they seem to have different causes and I'm not sure what my problem is.
I have been spraying at 4:1 mix (I realise this is likely the cause of my problem) and have tried to thin it down a little but need to try this again as the results weren't definitive. I have encountered some spitting/spluttering.
As stated I'm still working through solutions but thought someone may have sprayed hard shellac before or be able to identify my issue from general spraying knowledge.
Thanks in advance and apologies if I have missed a previous post on the topic.
Ben

[OfficialHorvath]

Hi, I haven't sprayed hard shellac, but generally the causes of these craters and fisheyes will be something that prevents the paint from adhering evenly to the substrate. The solution will come down to carefully evaluating your current prep of the surface before spraying and looking for possible causes, eg, start with the type of sandpaper you are using and what are you using to wipe off etc. Hope this helps. BTW my spraying experience is mainly with automotive type paints, but the principles will be the same - eliminate contamination sources.

[kiwigeo]

Another potential source of contamination is some of the non slip mates that people seem to love. Some of the mats are contaminated with the silicone mold release used during their manufacture.

Hi, I haven't sprayed hard shellac, but generally the causes of these craters and fisheyes will be something that prevents the paint from adhering evenly to the substrate. The solution will come down to carefully evaluating your current prep of the surface before spraying and looking for possible causes, eg, start with the type of sandpaper you are using and what are you using to wipe off etc. Hope this helps. BTW my spraying experience is mainly with automotive type paints, but the principles will be the same - eliminate contamination sources.

[Trevor Gore]

....And yet another potential source of contamination is oil in the air from your compressor.

[benldwyer]

Hi Gents, thank you all for your time and insight.

I have been very careful to use clean rags, hands and eliminate contaminants. I have a brand new compressor (oil free I believe) and inline filter at the gun. I do use those dodgy mats but not during or after sanding, but I will get rid of them anyway.

In the end I just had to take a step back, calm down, stop overthinking things and return to basics to solve the embarrassingly simple issue. Essentially it was the occasional splutter spitting onto the surface that was causing the craters. Air was getting in through the nozzle which wasn't tight enough, and after adjusting this, no more craters. Maybe the thick coats and warm dry weather in Perth contributed to them remaining in place and looking like fish eyes.

My next challenge is eliminating dust and lint. If I can do that I will save a lot of time not having to sand between coats. I have tried misting the work space (tent, see photo) with water, using different cloths (tack, shammy) but cant seem to prevent it. Is it possible without a professional both or does everyone generally have to do some sanding between coats?

Thanks again for your time and advice,

Ben

[asgilbert]

Hey Ben, Work look great mate. And an A+ for the amount of effort you go through. I have a booth with extraction but even that pulls dust/dirt from the surrounding area.

[benldwyer]

Thank you for your kind words an input mate, I'll keep working and try to improve my process.
Thanks again,
Ben

[Dave M]

So Martin is this a fact about the non slip mats? I hadn't heard that. It could be really problematic. They really are useful in certain processes but if you are right we need to stop using them.

Best Dave

[kiwigeo]

I had issues with french polish on an early build which I suspect was due to the rubber mat I had under the guitar. I suspected the mat after reading comments either in here or in GAL magazine. Silicon is often used in spray on release agent used in molds.

So Martin is this a fact about the non slip mats? I hadn't heard that. It could be really problematic. They really are useful in certain processes but if you are right we need to stop using them.

Best Dave