# Amount of Lacquer and Thinner needed for large area?



## Chems (25 Jun 2009)

I've tried working this out using calculated methods but I don't trust the numbers. I have a large piece of furniture:




And I want to lacquer it, straight off no sealer first how much literage of lacquer do people think I'll need to coat this big boy?

And secondly seen as I'm planning on spraying the finish does anyone know the rough calculation for cellulose thinner to lacquer. 

I know this is quite a vague question, but I think I'll need the 5 litres of Chestnut melamine lacquer but I just wanted a second opinion, and a 3rd or 4th if possible. TIA


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## Sgian Dubh (26 Jun 2009)

I calculate as follows-- the text in the paragraph after this one is an extract from a document on estimating for furniture makers I created some time ago. It's a little on the generous side, but I find it's best to buy a little too much polish than too litle.

"The coverage of nitro-cellulose type finishes such as pre-catalysed lacquer and acid catalysed lacquer is approximately 60 ft² per litre, which is roughly the same as 6 metres² per litre. Applied as per most manufacturers recommendations of a wet film between 100 and 125 microns (µm) thick this gives a dry film thickness of about 50 µm after the solvents have evaporated and the finish is fully cured. Three coats applied in this manner results in a total dry film thickness of approximately 150 µm. Pre-catalysed lacquer type finishes should not be thicker than this because thicker films fail with cross grain cracking or the even worse ‘Chinese writing’ showing up weeks or months later. To provide a sense of scale a typical human head hair is approximately 100 µm thick. Therefore three coats applied over a surface area of 5.5 m² needs approximately 2.75 litres of polish, i.e., (5.5 m² X 3 coats)/ 6 m² per litre = 2.75 litres."

I seldom use the sanding sealer provided by the manufacturers under pre-catalysed lacquer. I use the top coats as their own sealers. Sanding sealers are convenient in a mass production environment but they tend to be a bit softer than the top coats. If the job is big enough I use gloss to seal followed by one coat of the sheen required. I generally prefer to get the finish on in two wet applications at about 125 to 140 µm each, unless the wood is open textured. For these I usually apply a coat with extra thinner in it (about 15-20%) at about 50-75 µm thick to seal the wood fibres and to prevent air bubbles backing out of the open pores which will spoil the two subsequent coats applied at about 100 µm each. 

In response to your second question I generally add between 5% and 10% lacquer thinner to pre-cat lacquers. If it's very hot and dry I sometimes add a little lacquer retarder. The amount of thinner required depends on your spray set-up and the viscosity of the finish coating straight out of the can. In my case I use a low pressure turbine delivery system connected to an Asturo HVLP gun with a 1.2 mm needle and nozzle.

The polish manufacturers can tell you the requisite viscosity for spraying their polish if need be, and the recommended needle and nozzle size, and you can test viscosity with a viscosity cup. I don't use a viscosity cup nowadays because I can generally tell if the stuff is the right viscosity for spraying by watching how it runs off a stick-- a steady unbroken stream is what I look for, not thick and gloopy, nor thin, broken and dribbly. Slainte.


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## Chems (26 Jun 2009)

Thanks for that, I think I'm going to need a lot then for the required 3 coats.


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## Sgian Dubh (27 Jun 2009)

Chems":1lhhrktt said:


> Thanks for that, I think I'm going to need a lot then for the required 3 coats.



About 10 or 12 litres should be more than enough.

I eyeballed the job as follows:

Vertical panels: 8 faces at 2m X 1m
Horizontal panels: 6 faces at 2 m x 1m
Back panel/drawer parts/odds and ends: 2 faces at 2m X 2m

Do the numbers and you get 36 m2, ie 16 + 12 + 8= 36. Then the sum is (36 X 3)/6 = 18 litres. 

The numbers I used are an overestimate; your cabinet is smaller than that. And in truth polish coverage should be closer to 8 m2 per litre of polish, not 6 m2 per litre, so you could calculate (36 X 3)/ 8 = 13.5 litres. Use actual dimensions derived from measuring your cabinet parts and I bet you only need about 10 litres of a pre-cat lacquer at £23.50 inc VAT per 5 litre can, plus a litre or so of lacquer thinner and a litre of gunwash; about £55 in total for your polish needs for that job. Slainte.


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## Chems (28 Jun 2009)

I was planning on using Chestnut melamine lacquer with is £50 for 5 litres, so if I'm going to need closer to double that what type of lacquer and thinner would you recommend I buy? 

Thanks again for the advice, totally in the woods at the mo.


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## JonnyD (28 Jun 2009)

I usually use morrells woodfinishes and i think the nearest branch to northampton is leicester. You may have to pretend to be trade though.

Another option is here

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

If you scroll down a bit you can get 5L of precat for about £22 plus vat. This may be they best way to go. The guy from the company posts here so maybe he could advise you better.

Jon


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## Sgian Dubh (29 Jun 2009)

Chems":2x2tj2ul said:


> I was planning on using Chestnut melamine lacquer with is £50 for 5 litres, so if I'm going to need closer to double that what type of lacquer and thinner would you recommend I buy?
> 
> Thanks again for the advice, totally in the woods at the mo.



I have no practical experience of Chestnut products so I cannot comment on their performance during either application and over time. Their prices seem about on a par with similar products from other companies.

The finish I turn to most often for quick effective results with decent durability is pre-catalysed lacquer at about the prices Jonny mentioned. If I need something more durable in a standard spray finish I go for one of the two pack AC lacquers or a two pack AC polyurethane type. Each of these cost about £7 or £9 more per 5 litre can than regular pre-catalysed lacquer.

All the polish suppliers offer good products-- they have to or they go out of business. You just need to select your preferred one, eg Chestnut, Fiddes, Morrells, Smith and Rodger, etc. I mostly use Morrells products for the simple reason that they have a distribution centre in town. Slainte.


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## BradNaylor (29 Jun 2009)

From a quick look at your piece of furniture and without making any precise calculations I would say that two 5-litre cans would be sufficient.

I use Morrells AC lacquer but you may find pre-cat easier to use. A bit like Richard my choice of Morrells is largely because their factory is only a couple of miles from me. Perversely though, I now have to drive 10miles in the opposite direction to get to their neearest trade counter!

A tip;

Morrells are for trade only. You will have to prove your trade credentials by producing a business card you have knocked up on the computer beforehand.

You will also have to negotiate a discount in order to get realistic prices. I get 40% across their range - this seems fairly typical.

Cheers
Brad


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