cutting and polish over laquer

[mongrell]

giday all am spraying a freeform sculpture type thing with 50 50 single pack laquer ,trouble is i get over spray on parts ive allready sprayed .ive got some eee ultra shine ,would using this work ?i dont want to end up with a high gloss and how do you apply it with a rag or fine paper

[rsser]

What do you mean by overspray? Pimples? Runs?

If so, no. Not at least without a lot of work.

If more gloss than you like, try rubbing back with 0000 steel wool. Or EEE might work to dull the surface but try the steel wool first.

[mongrell]

rough sandpaper feel because of piece behind being to far away from gun

[MacS]

To "reflow" lacquer get some "lacquer retarder," it will flow out the overspray.

You add it into your lacquer thinners and then into your lacquer, you can add up to 10 %. In a warm climate less, in a cold shop a little more.

Some, sprayers use retarder all the time, as it increases the flo-out.

[mongrell]

is this put in the origanal laquer ? ive never heard of it

[MacS]

Mongrell,

Yes, most coatings have some solvents that are used to slow down the drying, which will increase the flo-out, and these retarders are compatible with the other components that make up each coating.

Examples of retarders.
Propylene glycol - is a water base retarder.
Polyethylene glycol – is a solvent based retarder.
Dimethylene – is a solvent for water or oil colorants.


Ask, the company that sold you the Lacquer, they will know eactly what I am referring too.

You mentioned you used a 50 -50 mix, most coatings today are "ready for use" which means, you cannot add thinners to the coating because of the VOC restricions or you will be in violation of the codes.

Do they have VOC compliance coatings over there.

Mac S

[durwood]

You can add as much thinner as you like to lacquer, the reason you are getting dry spray is that you are not thinning it enough and the air is drying it out too much before it reaches the surface. If you thin the lacquer down more it will be wetter when it hits the surface, you can even spray straight thinner on to remelt the lacquer if you need to.

There are other ways of getting the surface smooth after you finish spraying as well. Lacquer is the easiest material of any to spray as long as you understand what you can do.

How far away from the gun is the surface?

If you can show us a photo of the object you are spraying may be able to show you how to go about spraying it without dry spray in areas.

[MacS]

Can someone answer these questions

Ask, the company that sold you the Lacquer, they will know eactly what I am referring too. "DO THEY SELL RETARDER DOWN THERE ?"

You mentioned you used a 50 -50 mix, most coatings today are "ready for use" which means, you cannot add thinners to the coating because of the VOC restricions or you will be in violation of the codes. "DOES THIS APPLY IN YOUR COUNTRY ?"

Do they sell VOC compliance coatings over there.? "MOST VOC COATINGS CONTAIN SOME RETARDERS"

Thinning out lacquer with 50% or more with lacquer thinner will reduce the amount of solids you are applying on the timber taking more time to complete the finish, plus lacquer thinners dries so fast it would not flo out the overspray, it would make it worst. You need a slower drying solvent, not more thinners

Retarders, are also used to remove "blushing in the coating due to high humidty", by allowing the trapped moisture (BLUSH) in the coating to excape.

They must sell retarders if they sell nitrocellulose lacquers.

[mongrell]

mac by 50 50 i mean 50% gloss 50% flat .things must be differant over here we buy laquer and thinners seperately and mix our own im mixing 1 part thinners to 4 parts laquer. went down paint shop and what they told me was penetrol is retarder . overspray is very light so ill try to rub it out today wanted to let it harden a couple days

[durwood]

MacS,

Yes, you can get retarder thinner here.

We Don't have the VOC regulations that are in force in the States.

Nitro Cellulose lacquer is sold as a concentrated product and is reduced with with its own thinner, usually the ratio is 60% thinner to 40% NC lacquer but now manufactures have some produces that vary from this. It can then be sprayed and reduced further if you need to especially if you are repairing sections.

The retarder is also added only in the amount of about 10% as you said to prevent the lacquer drying so fast in hot weather or to help prevent blushing in cold or wet weather. It is very expensive and even though I have it in our store it is hardly ever needed as we have a climate controlled spray booth. Using it slows drying times down so its only used ocassionally

As our weather is fast approaching summer it shouldn't be necessary for Mongrell to buy any just don't spray if the weather is lousy. It sounds like he may be hard pressed to actually get some where he lives and would have to specially order it from Melbourne. Penetrol is NOT retarder.

Mongrell, your sculpture looks great, it appears to be pretty glossy in most parts and you shouldn't have much trouble getting to any areas with a gun.

So rub back the dry spray with some fine paper,

Thin the material more than you have, in your case the mixing ratio of the product you have seems to be close to what you need so go about 20% extra (if you have put on 3 coats or more).

Use as little air pressure as you can, depending on the gun you shouldn't need more than 40psi but if you don't have a spray gun set up for lacquer it may want to spray the lacquer dry. 2 pack guns have a ratio of more air and less paint so this may be one of the reasons you are getting dry spray. Don't hold the gun too far away spray it on wet.

Because of the shape of the sculpture it is going to be difficult to not get some dry spray on areas as you spray others but if you keep the lacquer thin it will be difficult to get thick sandy dry spray.

As a lot of your sculpture is thin set the fan to a narrower width when you are spraying them, so you don't have lacquer going past the bit you are spraying. Narrowing the fan means you also need to cut back the amount of material coming out of the gun by turning in the know behind the needle a bit and moving the gun away from the surface being sprayed.



If you look at the following post you will find some instructions on how to remove and dry spray you can't avoid and get the smooth finish you want.

http://www.woodworkforums.ubeaut.com.au/showthread.php?t=19490&highlight=durwood&page=2

I have to disagree with MacS about thinners not flowing out the overspray, its used exactly for that reason, when you spray a large area the lacquer does dry really fast ( so fast it can dry before it gets to the surface if you hold the gun too far away) it will melt the dry spray down as well as the smooth lacquer around it making an invisible repair. ( provided the overspray is not really big dry and sandy) . This is one of the great things about lacquers (acrylic lacquer also)

You can finish a surface, some mug can come along and damage it and you just spray on more material over the damage thin it down and then spray thinners over the dry and wet edge to make the surface one complete coating again. Great if you have a large panel and small damage in the middle

A touch up gun was designed for that sole purpose.

MacS, retarder could be used also but you then have a surface that takes far longer to dry. The retarder slows the paint drying so it needs less heat as it dries so any heat in the air helps keep the moisture from falling onto the surface.The blushing is actually a coat of moisture ( like dew) which falls on the lacquer.

[mongrell]

thanks mac and durwood thats cleared up a few questins .tried the 0000 steel wool today and that fixed the overspray .also dulled it back to somewhere where i want it

[MacS]

Yes, it will take longer to dry, that is the reason it is used, fast drying solvents in certain conditions can cause the overspray, because they dry too fast.

Let's say you were spraying cubbies, or inside cabinets, unless you know the trick on how it is done, in most cases you will end up with overspray inside the cabinets, and you will have to try reflowing it out, in most cases you get the bades sides fix, but then the good parts now have the overspray.

If you added a little retarder, it would flow it out because it opens up the lacquer longer giving it better flow out

Depending on how much is added, where talking only hours, its certainly better then rubbibg or sanding, or respraying.

Just about every shop that sprays, has retarder, take my word for it.

[MacS]

Now, that I know that 50 -50 means half of one sheen and half of another. I now also know know that your lacquers are not VOC compliant, because you mix your own coating and thinners.

What, is the "solids content" of your lacquers? This would be very important to the mixture of your coatings. As an example, if the solids was 13 % and you reduce it 50-50 you would shooting very little solids, because you not only reduce the lacquer down to 6 1/2 % solids, its actually less, because if the solids content was 13% in the coating, there would also be more solvent too, this would be besides the other additives that normally are in the Lacquer.

I would appreciate if only "sprayers" answered this question for now, because normally sprayers don't know, because no one ever told them about the "solids content" in the coating, the only material that remains on the wood is the "solids content".

The more solids in the coating the better the build, and the less coats you will need to apply.