# Spray finishing novice - advice please



## Aled Dafis (7 Jun 2009)

Hi, I fancy having a go at spray finishing, but don't really have much idea about how to go about it. I'm looking to apply a clear finish to small furniture projects.

I have a small compressor but no spray gun at the moment. Would a small touch up gun work for small jobs? I'm thinking of getting something like this.

http://www.axminster.co.uk/product.asp? ... =1&jump=44

Before anybody suggests, I can't stretch anywhere close to buying DeVilblis kit.

Also I need some info on what finishing product to use. From what I've read, the new waterbourne laquers perform well, and do away with all the fuss of thinning and cleaning with solvents. Can anybody point me towards a specific product and where to get hold of it.

Cheers

Aled


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## Fergus (7 Jun 2009)

I have the original Badger model of that gun -bought it years ago before all these smart repair guns came in. Firstly the trigger is very odd to use ,so in my opinion you would be better off getting a gun of more conventional design. At least that way any technique you build up can be used on other guns easily.

Peronally I would also go for a gravity fed gun ,as gravity helps force the product to the needle rather than suction. Also I see you mention waterbased,well most waterbased coatings are very viscous relative to solvent based coatins,so I would bear that in mind .

Having said that I have bought quite a few cheapie touch up guns on ebay ,so that when they are a bit knakcered I can throw them ..cheaper than spares..I save my decent guns then for the better jobs etc.

random ebay gun

^^ thats the sort of guns I have bought for doing little bits with and on the whole they are pretty good for the money-just dont expect Iwata/sata/Devilbis etc quality - as always you get what you pay for! 

Hope that helps a bit


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## Woodfinish Man (8 Jun 2009)

Morning Aled,

There are a number of lacquer manufacturers throughout the UK including Becker, Sonneborn & Rieck and Morrells. The one we recommend is produced by ISF and is a cracking sprayable finish called Aquabuild. You can source it through the following link

https://vault2.secured-url.com/frenchpo ... quers.html

I really hope this helps.

Ian McAslan


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## Aled Dafis (8 Jun 2009)

Thanks Ian, that looks to be just what I'm looking for.

I'll file the info for when I need to go about spray finishing, which may well be on my next project - an oak sideboard.

Would you suggest a sanding sealer first? How many coats will I need, and also what do the % sheen levels look like? I assume that 10% is pretty matt, whereas 90% is a gloss finish.

Cheers

Aled


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## Woodfinish Man (9 Jun 2009)

No problem Aled,

There's no doubt that using the sanding sealer first will produce a better final finish as the sanding agent makes it much easier to sand. However it's not imperative and you can use the Aquabuild topcoat, coat on coat. We normally recommend 1 coat of SS followed by 2 coats of topcoat, or 3 coats of topcoat. As you say 10% is classified as Matt then goes up to 25%,35%,50% and 90% being full gloss. We classify 35% as Satin and 50% silk.

Ian


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## Sgian Dubh (11 Jun 2009)

Woodfinish Man":10tnh3e0 said:


> We normally recommend 1 coat of SS followed by 2 coats of topcoat, or 3 coats of topcoat.
> Ian



Ian, I took a look at the products you sell and note that most of your pre-cats, post-cats and waterborne finish recommend a film thickness of 150 μm. Am I right in thinking this refers to the total dry film thickness and not to the wet film thickness, and that the recommended wet film application per coat should be in the region of about 100- 150 μm?

What happens if the total dry film thickness exceeds by much the 150 μm recommendation? Is this likely to result in film cracking, primarily across the grain, or the even worse Chinese writing, and which of the finishes are most prone to these tendencies? For instance, my experience is that the pre-catalysed and post (acid) catalysed lacquers are candidates for cracking problems, whereas old fashioned nitrocellulose lacquers are not. 

And how do your waterborne clear coatings perform if they exceed this film thickness suggestion? However, I must admit that I gave up on waterborne finishes back in the mid or late 1990s due to their tendency at the time to milkiness or cloudiness and their slightly cold blueness. I suspect that one of these days I'll again have to investigate their performance as the chemical formulation and finishing technology has moved on since then. Ta. Slainte.


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## wizer (11 Jun 2009)

Ian, I know you offer training on French Polishing. Do you plan on offering training for spraying techniques? That'd be a course I'd be interested in. Especially to see the types of finish with my own eyes.


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## Woodfinish Man (11 Jun 2009)

Hi SD, you definitely know your stuff.



> recommend a film thickness of 150 μm. Am I right in thinking this refers to the total dry film thickness and not to the wet film thickness,



You are absolutely correct the 150 microns is a dry film weight over 3 coats which will produce 0.06 inches of dry film.

Wet application should be 3 coats of 100 microns which will result in the same dry film thickness.



> What happens if the total dry film thickness exceeds by much the 150 μm recommendation? Is this likely to result in film cracking, primarily across the grain, or the even worse Chinese writing, and which of the finishes are most prone to these tendencies?



Spot on once again. Too thick a coat will result in trapped solvent, leading to stress in the film and subsequent cracking. In our experience PC & AC lacquers do not crack if thin coats are applied.




> And how do your waterborne clear coatings perform if they exceed this film thickness suggestion?



They will just go milky and take longer to dry out. There's no doubt that Waterbased technology still has a way to go to match its AC & PC counterparts but we've been impressed with Aquabuild. You're right it does produce a slightly dead, anemic appearance but so long as thin coats are applied it can be sanded and recoated at a push after 40 mins.

I really hope this helps.

Tom, we've been discussing starting spraying courses up here - it seems only a natural progression from our french polishing courses. The only problem is that our spraying facilities are not ideal and could probably only accommodate 2 attendees. Our technical chap here Drew is keen and so all I can say is watch this space - we're going to try to put something together and perhaps make changes to our premises.

What would you like to be included? AC. PC & Waterbased products along with grainfilling & shade matching? Any feedback would be most welcome.

All the best 

Ian


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## Sgian Dubh (11 Jun 2009)

Woodfinish Man":2rquzn5e said:


> There's no doubt that Waterbased technology still has a way to go to match its AC & PC counterparts but we've been impressed with Aquabuild. You're right it does produce a slightly dead, anemic appearance but so long as thin coats are applied it can be sanded and recoated at a push after 40 mins.
> 
> Ian



Thanks for the information. All useful to me.

Re the deadness of waterborne finishes. What is your experience of using clear dewaxed shellac under them? The occasional times that I do use waterborne finishes it's my experience that shellac warms up the finish and, because it's dewaxed, there aren't adhesion problems, as long as you also keep away from stearated abrasives for de-nibbing, etc. 

In truth, shellac to me is the universal 'go to' first coat under just about any other film forming polish if there are any suspicions of contamination (wax, oil, silicone), adhesion problems, resins, etc in the prepared wood. Slainte.


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## Woodfinish Man (11 Jun 2009)

Agree 100% - SHELLAC RULES!

It's brilliant under nearly everything in fact we sell a large quantity of de-waxes shellac to flooring contractors who apply it over old floors as you say to seal in old stains, waxes etc.

It's such a great product, so many different coatings can go over it with no problem. It produces such a lovely warm appearance (another reason why the flooring guys like it under our waterbased floor finishes). 

I'm so sad, I've even set up a shellac appreciation society group on facebook! 

Ian


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## Sgian Dubh (13 Jun 2009)

Woodfinish Man":3l0pnvfa said:


> Agree 100% - SHELLAC RULES!
> 
> It's brilliant under nearly everything ... It's such a great product, so many different coatings can go over it with no problem. It produces such a lovely warm appearance (another reason why the flooring guys like it under our waterbased floor finishes).
> Ian



I was hoping you might agree with my fondness for shellac as a universal base coat. 

Incidentally, I do believe you missed a zero in your earlier post. 150 μm is a little less than 0.006 inches or 0.15 mm, not 0.06 inches which is nearly 1.5 mm.

A useful size guide for anyone struggling work out what a μm (micometre or micron) is then a typical human head hair is approximately 100 μm in diameter. A micron is one millionth of a metre. Therefore when spraying pre-cats, post-cats, etc, each coat should be applied at just a bit more than the thickness of a human head hair, maybe pubic hair thick, ha, ha. Apply the stuff thicker than this per coat and, if you apply three coats, then your finish is likely to fail due to cracking or Chinese writing. Slainte.


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