Qualalac

I'm having a problem that is driving me nuts. I've been using qualalac and it is cracking. I mean lots of cracks. When I first noticed it I thought it was the wood but the cracks are in the finish. Moisture content in the wood is not an issue as the pieces that this is happening to are quite dry at about 6%. I'm mixing the lacquer with lacquer thinner 50% as per the directions. I'm using a small hvlp sprayer. I used to use nitrocellulose and never had a problem. I can't find it anymore or I would still be using it. Has anyone had this problem with qualalack or know what is causing this? TIA, Bob

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Reply to
turnerbob
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From Behlen's product catalog:

"Qualalacq? Thinner are recommended to be used in conjunction with this product."

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Reply to
Nova

Very nice work on your site.

Reply to
steven raphael

I've never used qualalac (in fact, I'm not even sure if that is the name of the laquer you're using or the wood!,) but I have used plenty of laquer, and experienced the same problem from time to time.

There are three main things that have caused a problem with laquer for me in the past, and one, all, or none of them may apply in your case.

The first two are related- excessive sunlight and/or heat when curing. I had a project not only crack, but even develop bubbles after laquering because I left it in front of a window on a hot, sunny day. Sometimes it's tempting to rush it, but laquer doesn't like being hurried (and it's really not that slow to cure in any case.) If you're setting it near a window, try putting it in the shade to dry.

The third is something I doubt you're doing, but here it is. Layered finishes- in my case, this happened when trying to exactly match an old, semi-transparent stain for a really picky customer who *wanted* the trim I was making for them to look old and (IMO) crappy. The only way to match the color was to do the same thing the original finisher did- to paint the stain on thick, and let it dry without wiping it off so it would deaden the grain pattern. When I sprayed the laquer over, it was able to slightly dissolve the stain that had cured on the surface, and ended up cracking pretty badly. The solution ended up being to paint the stain on, then follow that with a coat of shellac to act as a barrier between the stain and the laquer, and then laquer it. It looked like junk to me, but the customer was happy.

If there is something in the wood that is attacking the finish, you may want to try the shellac trick to seal it before the final topcoat. I used a 1/2 pound cut, and wiped it on with a clean rag. It will dry within minutes, and you can proceed to the final finish. If you're doing a really complex layered finish, I'd do this between each layer- the reason for the shellac is that it is alcohol based, and does not dissolve (or does not dissolve much) when it is covered by most commerically availible finishes.

Though of course, I'm still fairly convinced that finishing is more voodoo than science- the above is just what worked for me when I had the same problems with laquer cracking.

Reply to
Prometheus

Hi Jack, Yes I read that but I have a hard time believing that thier thinner is any different than any other lacquer thinner. I suppose there could be a difference. Certainly is a price difference. Problem is I've been using qualalack for about 6 months and the problem just started in the past couple weeks. I was looking at the spray gun this evening and I'm wondering if the air adjustment got turned. The air adjustment is very easy to turn and maybe it has gotten turned a little at a time.

Reply to
turnerbob

SNIP

Hi, Bob. First, really nice work on that website. I think that spalted maple bowl with the square edges is really pretty. Well designed, too.

The following may be more than you are interested in, but it might help others too. Me, I like to have as much info as possible, so here goes.

I'll try to hit the high points of your post with some ideas So that you won't think I'm just getting started in finishing, look at rec.woodworking under this same name, and you can see that I have written >extensively< on finishing (especially lacquers and urethanes), as well as on Woodweb. As a remodeler, I spray about 50+ gallons of lacquer on a heavy year (you read that right), and a little less than half on a lighter one. Along with industrial enamels and urethane coatings, I have had to break down and study, learn, practice and "trial and error" my way to finishing that I like.

I started finishing for myself many years ago when the people I had subbed the cabinet finishing to didn't do a good job and couldn't find their way to work except on Friday.

Anyway - there are a lot of different things that go on with lacquer and solvents. You are using a nitrocellulose lacquer, so you can use just about any brand of quality lacquer thinner that is out there on the market. Crown, Strip Ease, Sunnyvale, etc. are NOT quality thinners and who knows what they have in them. Not even the manufacturers know exactly. Many of these low end lacquer thinners are actually made from recycled materials, and are almost unusable with some finishes.

Buy a good quality branded lacquer thinner like Sherwyn Williams, Benjamin Moore, Startex, etc. There are others, and these are paint store items. cracking lacquer is difficult to do, so you may just have bad thinner.

Try thinning much less. The instructions on the can are guidelines, and they are a place to start when you are unfamiliar with the product. As a high VOC evaporative finish, lacquer will crack if it dried unevenly. Under certain conditions, say a warm dry area or an area with constant airflow or movement, the lacquer will begin to skin over. However, it won't look that way to the eye, and you can't see it unless you run your finger through it.

The finish cracks as the solvent attempts to outgas through the partially polymerized finish. The solvent looks for the weak spots in the "skin" and opens them up, pushing out the gasses through the cracks. A large amount of thinner (are you sure they said 50%??) will cause this to happen.

There could be contaminates on your wood. Stearated paper is notorious for screwing up good finishing. Many buy the cheapest sandpaper they can find, and overuse it. The lubrication (stearating compound - commonly known as a variant of soap) will come off the paper with heat, which of course is generated by sanding. This lubrication will actually melt into the wood and cause all manner of problems from patchy cracking to fisheyes.

I see that you do segmented work, and sanding down the different kinds of oily colored hardwoods as well as the resins in the glues will cause will generate a lot of heat and a lot of contaminates.

Try this: before finishing, clean the piece well with a rag wetted (not just damp) with lacquer thinner. Really scrub it. You won't raise the grain, and it does wonders for cleaning and will pick almost all the stearate up.

Thin less. 50% is just too much. You did not say if you were using an HVLP conversion gun (the type used with an air compressor) or a true HVLP, the type powered with a turbine. But in this instance, I don't think the problem is in the gun, as gun/pressure/delivery problems are all about the same. I have both types, and in moderate weather the thinning protocols for both types of gun are the same. Start thinning at about 25%, and see how that does.

Put the right amount of sealer on your piece. Normally, the manufacturers want about 3 to 4 mil minimum on a coat (some more) of evaporative finish, and it will dry to about 1 mil. It is important that you find the sweet spot for your finish, and that takes practice. (To run down how to make your test bed and records to establish the characteristics of each finish with your individual equipment, go to the rec. and search there).

Thinner than 3 mil will NOT give you a good finish unless you are up in the 5th-6th coat of material. For some build finishes a thinner coat makes a good topper, but we aren't talking about that here. The rule of thumb is that if you are laying down a thin even coat that is drying shiny, quickly and evenly as you are finishing, then you are not putting on enough material.

If you think your piece is contaminated with oils, stearates, or anything else you might have gotten on it when you handled it, then uses shellac. You quickly learn in fine finishing though, that shellac will dissolve or blur those gorgeous spalt lines in many woods. (THAT was an expensive lesson...) I would only use shellac as a primer if I knew there were problems with adhesion.

Lacquer is its own best primer. Nothing sticks to lacquer like itself. Why? Since lacquer is a build finish, properly applied coats will melt into each other making a monolithic finish. Do not mix any other coatings in between layers of lacquer for any reason as you defeat the reason it is used, and that is the ability to build a thick coating rapidly. If you put anything in between the coats, then you will have a film finish, or layered. This can easily lead to witness lines, poor adhesion, etc.

It is easy to have problems with the safest and most forgiving of all finishes, shellac. For example: Put a coat of shellac on wood for primer, sand and seal. Put a coat of shellac on top of that. But wait.. did you thin the shellac to spray it or brush it easier? If you did, you probably used alcohol from HD, Lowes's or the lumberyard, and it is only around 96 - 97% pure.

Why is that important? The other three percent is water, and that is the bugger to get out. This cheap alcohol is distilled from a number of products, again sometime of unknown origin. However, if you go to the paint store and buy anhydrous alcohol (99.99% pure) you are good to go on your thinner/solvent. No water introduced into the shellac. Sadly, this doesn't show up right away, as water is easily miscible with alcohol, so you may have to wait for the shellac to cure out completely before you see the problems.

As far as nitrocellulose lacquer availability, go anywhere they sell lacquer. If it isn't pre-cat, post cat, or CAB (non yellowing white with acrylic enhancement) and clearly marked as such, it will be nitrocellulose. Most of today's lacquers are pretty good quality and behave well under most conditions, so you should be good with something off the shelf, nothing from a specialty shop needed.

The common brands are Deft (old reliable), Old Masters (my favorite off the shelf brand), and there are a few others. Look for something in the upper teens to lower-mid twenties of solids in the ingredients when buying.

Good Luck! I hope you let us know how this all turned out.

Robert

Reply to
nailshooter41

I got a little confused and was thinking of Qualasole padding lacquer. Qualalacq is a sanding sealer. I don't think it's designed to be used as a final finish.

Reply to
Nova

Look again.

Reply to
CW

Oops, too many Quala...'s.

Reply to
Nova

Thanks Robert, A lot of good info in your post. The directions on the can do in fact state a 1:1 mixture. Thinking that might be the problem I cut back to 3/4:1 with the same result. I would guess the thinner I'm using is ok as I've used the same thinner with success in the past. With both qualalack and parks nitrocellulose. The can suggests a 35-50# setting. Being an inexpensive sprayer I has no idea what it is putting out. My question to you is could the air mixture in an hvlp system have anything to do with a poor (cracking) finish? While I've used the sprayer for a few years my experience is limited. Up until now its been point and pull the trigger. My guess would be to turn down the air while still maintaining an even flow. Thanks, Bob

Reply to
turnerbob

in fact state a 1:1 mixture. >Thinking that might be the problem I cut back to

3/4:1 >with the same result. I would guess the thinner

both qualalack and parks >nitrocellulose.

And thanks for responding, Bob. Sometimes you never know if anyone even bothered to follow the thread they started.

I am setting aside application technique in this as I am figuring if you have been getting acceptable results with your setup for years, you have put the time into that aspect of finishing to get it where you want it.

Turning down the air flow will only make the material droplets bigger, and give less of a consistent pattern.

New products have to be fine tuned to your equipment with you use HVLP, and it is much more critical than the old high pressure days.

Here's the easy way to set the gun up with a new finish. Take a sheet of plywood (anything smooth) outside and lean it up where you can see the finish in strong light. Turn on the turbine unit or compressor and set them at a pressure you have had good results with in the past.

Put some thinned material in the gun and close the fluid control valve completely. Walk over to the plywood and slowly open the fluid valve with gun in the proper spraying position. You should see tiny droplets, no mist. At about 8" from the surface, if you see more than just a very small amount of bounce back, turn down the pressure to the gun.

When it covers to a wet consistent surface easily, leave the fluid nozzle alone. Leave the pressure alone. Check your surface after your material has dried. On the area that you like the finish, add a second coat. If it looks good and stays good when dried, you are finished. I have three HVLP guns that do different things - each has a little nick in it on the fluid control for the different products I spray.

Anything is possible, but in this instance, the gun or the air delivery is not a likely suspect. Unacceptable delivery symptoms usually attributed to HVLP >equipment< can be

1) sputter - not enough air to the gun, fluid nozzle opened too high, product not thinned properly 2) uneven coating thickness - inconsistent delivery of air to the gun. This can be caused by dirty or blocked air filter, or air flow set too low 3) A splotch or splatter occasionally on the finish - not enough air to the equipment to properly disperse the particles (remember, HVLP doesn't atomize like high pressure) 4) #1, #2 and #3 above can also be caused by a dirty aircap assembly. Many times when people clean their HVLP systems they don't clean the holes in the horns, which are a precisely determined set of venturi that determine direction, pattern and dispersal of fluid droplets. I clean mine with a wooden toothpick, and the tiny holes with >one< bristle from a stainless steel brush 5) Fisheyes, craters and voids - while these are usually associated with poor surface prep, they can be attributed in some cases to gun cleaning. Many people use the same gun for both water based and solvent based products. Water, ammonia, and all kinds of things can be in the gun from using a water based product. This is classic cross contamination

Just about everything else happens outside of the gun, leaving only fluid materials and project preparation.

Cracking or crazing is not usually an application issue. To help bear this out, if you have been using this piece of equipment for years, I have to think you have been using it correctly or you would certainly have run into this before, no matter the manufacturer of sealer.

These annoying problems can be the bane of finishing. They take the fun out of it. When I am committed (by contract!) to do the finishing, and something like this cracking pops up, this is how I keep my head in the game: I ask myself - how much would I pay to get myself OUT of this mess and finish this project? $20? $30? $50?

Thankfully, for this kind of thing is a $20 science lesson. I change brands of lacquer ($10 for a quart of off the shelf stuff) and $8 for a gallon of good thinner.

In your particular case my best guess is the thinner is the culprit. Behlen's makes a good quality product line, although I am not personally familiar with qualalac.

Please understand that all lacquer thinners are not completely compatible with all lacquers. The Crowns, Sunnyvales, etc. are made from recycled mixtures and may have products in them that react differently with certain lacquer formulas. Those thinners will fine with some, not with others. That is the specific reason I use the above mentioned brands to clean the equipment (hence the term "gun wash" you have probably heard) but not to mix the products. Sometimes it just comes down to compatibility.

Since HVLP does not atomize, it is necessary to use products that can accept thinning well, and aren't too touchy about it. You should know (and probably do) that ALL manufacturers recommend their own thinners, retarders, flow controllers, etc., to be used with their product. This is without exception. But no finishers I know ever do unless it is economically feasible.

Since you have the Behlen's now, I would try thinning with a really good quality thinner. If that didn't work, for my own satisfaction I would change lacquers and try it first with the old thinner, and then with the new. Unless the lacquer you have is old, a bad batch, or has been improperly stored (not necessarily by you) or shipped, the answer should be in there somewhere.

It will be easy enough for you to find out.

Once again, let us know how this pans out. If it were me, I would spend the dough and get through this as quickly as possible.

Robert

Reply to
nailshooter41

do in fact state a 1:1 mixture. >Thinking that might be the problem I cut back to 3/4:1 >with the same result. I would guess the thinner

With both qualalack and parks >nitrocellulose.

Thanks Robert, Your input is very much appreciated. I think I'll try different thinner as you recommend. I didn't really think the air was the problem but I will go through the setup as you recomended just for peace of mind. In a way its kind of good that this happened. It got me back on usenet again. I used to come to rec craft woodturning daily for years and read every post. I'm talking way back when google was deja news. Heck I even remember Arch. Thanks, Bob

Reply to
turnerbob

Great couple of posts Robert- that filled in a couple of gaps I had, and is an excellent reminder of the process (I don't spray laquer from my cup gun very often- because I'm usually too lazy to want to clean it afterwards, and just use a rattlecan instead.)

Reply to
Prometheus

Hi Jack, Yes I read that but I have a hard time believing that thier thinner is any different than any other lacquer thinner. I suppose there could be a difference. Certainly is a price difference. Problem is I've been using qualalack for about 6 months and the problem just started in the past couple weeks. I was looking at the spray gun this evening and I'm wondering if the air adjustment got turned. The air adjustment is very easy to turn and maybe it has gotten turned a little at a time.

I don't know this specific product - I do know that with the automotive lacquers I use (on cars), the thinner is VERY different from the stuff I get at home depot, though both are called lacquer thinner. I have used the cheap thinner with DEFT that I get in gallon cans with no problem though

Reply to
William Noble

Without being familiar with the product, is there a chance that it just got old? I know I've got a can of shellac down in the shop that just will not cure anymore, no matter how long I let it dry. It just got old, and is no longer good.

Reply to
Prometheus

Thanks. I don't mind helping when someone is trying. And finishing can be very, very frustrating. I have worked on problems for hours (sometimes a couple of days) to get things ironed out. And in the end, there have been times when all is said and done I am not really sure why it worked out.

And as for that rattlecan.... what a lifesaver. I use them wherever I can! Touchups (hey - if you apply Deft from a quart can, it comes in a spray can for touchups, too!), small projects, lathe stuff (especially Christmas ornaments), etc.

I really like the "no cleanup" part of spray cans and the consistency of the finish. At 35% or less material delivery ($$$ !!) from a spray can, I don't go wild with the stuff but I wouldn't be without it either.

Robert

Reply to
nailshooter41

you don't need to clean a spray gun after using laquer if you just dedicate a spare gun to clear laquer only - if it gets plugged up, just spray a litthe thnner through it and continue - I've used the same gun for about 6 years, always keep laquer in it, only had to clean it once in that time

Reply to
William Noble

I have heard of this, but never tried it. I know for me, I don't want (or have the dough!) a $300+ gun dedicated to one finish. My work requires that I spray too many types of finish, so I am used to cleaning them, sometimes a few times a day . But I DO keep a different gun for water borne and solvent coatings.

And even though I shoot a lot of lacquer, my formulas for retarding and thinning are different (similar) for every type of weather. I don't want to pick up a gun and load it if I has anything other than the mix I am spraying for the day. For me it is easier to start with a completely clean slate than a >pretty< clean one.

When I have a full day of spraying, one trick I learned (really frowned on by the product reps) is to put about 1/2" of the appropriate thinner in the bottom of a 5 gallon bucket and snap the lid on between coats. It keeps the area around the aircaps ready to go and prevents any drying of the coating.

Robert

Reply to
nailshooter41

What do you do, just dump out the cup and run laquer thinner through it when you're finished, or actually store the laquer in the cup?

Sometimes, that would probably work out great for me, but if I didn't need to laquer anything for six months or something, I wouldn't think storing it in the gun would be a very good idea!

Maybe I'll get it out and give that a try- worst thing that could happen would be a nasty clog, and a couple days soaking in thinner would *hopefully* take care of that. If it works, it would save me a bit of money in finishing products, if not, it'd just be a PITA to clean once.

Reply to
Prometheus

Might work for me, though- laquer is the only thing I spray from the gun (most other things can be brushed on successfully), and it's not a super high-end piece of equipment in any case. At $80, it's not junk- but it's definately not in the same league as some heated true HVLP rig.

Like a lot of guys in woodworking (or metal working for that matter), finishing is sort of a chore for me. I make a point to always do my level best at it, and research it before doing something new, but it's really not something I *want* to spend a day doing!

And that is one of the main differences between a hobbyist and a pro- if you're shooting laquer everyday, you're bound to have preferences like that. For me, I just get it close and tweak things until it looks good enough. That's the beauty of no longer doing this stuff for a living- the one or two things I'm coating are never really that big of a rush, because there usually is a week or two between side jobs. That, and I almost never have a full shop full of trim to spray- though I will next week (I'm milling some custom ash trim for a guy at work), which is why your run down was greatly appreciated!

Not sure what you mean- are you putting the thinner in the bottom of the bucket, then setting the open can of finish in there as well before snapping on the cap so the fumes keep the finish from skimming over, or putting the gun in there?

If it's the latter, I use a similar trick, but I like yours better. I always just splashed a little thinner inside of a plastic grocery bag, then stuck the gun in that and wrapped it up tight before lunch, between coats, etc.

Reply to
Prometheus

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