spraying shellac with an hvlp -- bad results
This is the first time I've tried to spray shellac. It was bullseye, out of
the can, and I cut it with denatured alcohol. I sprayed it, and it looked ok at first, but as it dried, it seemed to pucker in spots and give me orange peel. It's acting like I put it on too thick, but when i tried to lay it on thinner, it didn't seem to be atomizing correctly, and it went on a bit spotty. I put it on heavier to make it flow, but then it didn't seem to dry right. What did I do wrong? Not thin enough? |
Mark,
I sprayed the same shelac a few weeks ago. I used my latex tip and did not thin it and only got a real fine orange peel - overall a nice finish. I am going to thin it a little next time. P.S. You can buy extra tip kits on ebay for much less than the other sources. Good luck, AZCRAIG www.azcraig.us "mark" wrote in message ... This is the first time I've tried to spray shellac. It was bullseye, out of the can, and I cut it with denatured alcohol. I sprayed it, and it looked ok at first, but as it dried, it seemed to pucker in spots and give me orange peel. It's acting like I put it on too thick, but when i tried to lay it on thinner, it didn't seem to be atomizing correctly, and it went on a bit spotty. I put it on heavier to make it flow, but then it didn't seem to dry right. What did I do wrong? Not thin enough? |
What make HVLP are you using? This sounds like gun/turbine problems.
-- Rumpty Radial Arm Saw Forum: http://forums.delphiforums.com/woodbutcher/start - - - - - - - - - - - - - - - - - - - - - "mark" wrote in message ... This is the first time I've tried to spray shellac. It was bullseye, out of the can, and I cut it with denatured alcohol. I sprayed it, and it looked ok at first, but as it dried, it seemed to pucker in spots and give me orange peel. It's acting like I put it on too thick, but when i tried to lay it on thinner, it didn't seem to be atomizing correctly, and it went on a bit spotty. I put it on heavier to make it flow, but then it didn't seem to dry right. What did I do wrong? Not thin enough? |
"Rumpty" wrote in message ... What make HVLP are you using? This sounds like gun/turbine problems. porter cable conversion gun. Seems to work fine on lacquer, but that's all I've ever sprayed with it. |
Hi Mark,
If you have to put it on thick to make it flow makes me think that you are not atomizing the material well enough. So try it with more atomization pressure. If this does not do the trick, thin it more. I find that even with a crappy gun I can spray a 1.5 lb cut with no problem. Good luck, JG mark wrote: This is the first time I've tried to spray shellac. It was bullseye, out of the can, and I cut it with denatured alcohol. I sprayed it, and it looked ok at first, but as it dried, it seemed to pucker in spots and give me orange peel. It's acting like I put it on too thick, but when i tried to lay it on thinner, it didn't seem to be atomizing correctly, and it went on a bit spotty. I put it on heavier to make it flow, but then it didn't seem to dry right. What did I do wrong? Not thin enough? |
Two possible causes: shellac needs more thinning for your
gun/tip/pressure combo. You are spraying from too far away, allowing the shellac to dry before it hits the surface. Practice makes perfect. Try altering your technique. What size tip are you using? David mark wrote: This is the first time I've tried to spray shellac. It was bullseye, out of the can, and I cut it with denatured alcohol. I sprayed it, and it looked ok at first, but as it dried, it seemed to pucker in spots and give me orange peel. It's acting like I put it on too thick, but when i tried to lay it on thinner, it didn't seem to be atomizing correctly, and it went on a bit spotty. I put it on heavier to make it flow, but then it didn't seem to dry right. What did I do wrong? Not thin enough? |
First thing to do is to dump the idea that there is something wrong with
the unit. It'll save you some time. Cheap low quality HVLP conversion systems can be the cause of a lot of problems with product applications. That is why the question was asked. -- Rumpty Radial Arm Saw Forum: http://forums.delphiforums.com/woodbutcher/start - - - - - - - - - - - - - - - - - - - - - "MikeG" wrote in message ews.com... In article , says... This is the first time I've tried to spray shellac. It was bullseye, out of the can, and I cut it with denatured alcohol. I sprayed it, and it looked ok at first, but as it dried, it seemed to pucker in spots and give me orange peel. It's acting like I put it on too thick, but when i tried to lay it on thinner, it didn't seem to be atomizing correctly, and it went on a bit spotty. I put it on heavier to make it flow, but then it didn't seem to dry right. What did I do wrong? Not thin enough? First thing to do is to dump the idea that there is something wrong with the unit. It'll save you some time. Next thing to do is to get the viscosity cup recommended by the maker. Ford, Zhan then contact the maker to get an idea of what should flow out of the cup and recommended needle/nozzle combination. What you could be doing wrong could be not spraying the right viscosity for the needle/nozzle combination, to much air pressure, to little air pressure, too much air volume, too little air volume, incorrect fluid flow, needle set too far out from the nozzle, needle set too far into the nozzle, or any combination of the above. It's unlikely that even a three pound cut of shellac would need thinning but with the viscosity cup you will at least have an idea of where to start. If you know you have the right viscosity and needle/nozzle combination all you have to do is play with the air volume and fluid flow and needle set. The alternative is playing with all the factors in the rather large number of combinations they present.In other words without at least some fact based info you are just ****ing in the dark. -- MikeG Heirloom Woods www.heirloom-woods.net |
"MikeG" wrote in message ews.com... In article , says... This is the first time I've tried to spray shellac. It was bullseye, out of the can, and I cut it with denatured alcohol. I sprayed it, and it looked ok at first, but as it dried, it seemed to pucker in spots and give me orange peel. It's acting like I put it on too thick, but when i tried to lay it on thinner, it didn't seem to be atomizing correctly, and it went on a bit spotty. I put it on heavier to make it flow, but then it didn't seem to dry right. What did I do wrong? Not thin enough? What you could be doing wrong could be not spraying the right viscosity for the needle/nozzle combination, to much air pressure, to little air pressure, too much air volume, too little air volume, incorrect fluid flow, needle set too far out from the nozzle, needle set too far into the nozzle, or any combination of the above. This just about covers everything that *could* possibly be wrong, so it really doesn't narrow things down for the OP. If there's orange peel then the only reason for that is a first coat that is too dry followed by wetter coats that the sprayer attempts to flow on. That's what creates the orange peel - subsequent coats bridge the spotty coverage of a dry coat and create the humps we call orange peel. You can't fill enough with additional coats and it will always look worse after it dries than it does when it's wet. Thinning the fluid should be per the manufacturer's spec. It's usually ok to thin a bit more if the gun does not seem to spray it freely, but generally starting with manufacturer's spec is a very safe starting point. Air flow, pressure, etc. are easily adjusted by shooting at a scrap and adjusting to get a good fan and a good coverage. You should easily be able to flow enough to cause a run if you just hold the gun in one place. Spray with a slow, steady pattern, just overlapping each pass. You should imagine that you're stretching a thin film of that clear stuff that wives keep in the kitchen cupboard and that *only* wives can properly stretch over a bowl of leftovers, over your workpiece. One pass on an area. One pass. Not two. Not a little touch up. One pass. End to end. Watch your flow as you're laying it down. You'll see if it's going on too heavy. You want to see it flow on. Let it tack up per the manufacturer's spec between coats. No shortcuts here. Smoke a cigarette, load the woodstove, instruct the wife in the art of changing car tires - whatever is necessary to distract you while you give that coat the required flash time. Then you can put on another coat. Flash times and dry times are going to be affected by temperature and humidity, as well as how thick the coats are. A good wet coat is thicker than a dry coat, but not so thick that you should see protracted dry times. It's not that you're trying to put it on thick, you're trying to put it on wet. Keep that though in your mind. Remember the plastic wrap idea. Most folks make the mistake of spraying too fast as they fear runs. Spray too fast and you get dry coats which result in orange peel. It sands out, so it's not the end of the world, but it is extra work. It's unlikely that even a three pound cut of shellac would need thinning but with the viscosity cup you will at least have an idea of where to start. If you know you have the right viscosity and needle/nozzle combination all you have to do is play with the air volume and fluid flow and needle set. Agreed the viscosity cup can be helpful, but the same can be achieved by spraying at a scrap target and observing the fan. It's all a matter of what makes you comfortable. I wouldn't want the extra step of the viscocity cup, but others may well prefer to go that route. The alternative is playing with all the factors in the rather large number of combinations they present.In other words without at least some fact based info you are just ****ing in the dark. Not really. Again, you have the starting point defined by the manufacturer. Thin to that point and start spraying on a scrap. Adjust the gun and tackle the workpiece. There is no shooting in the dark, ****ing in the dark - (by the way... if you're going to **** in the dark always make sure you know where the electrical outlets are), it's just a simple matter of setting up the gun. That's something you have to do anyway. -- -Mike- |
Excellent advice for the OP, Mike. Much more focused response than some
of the others who prefer the "shotgun approach". David Mike Marlow wrote: "MikeG" wrote in message ews.com... In article , says... This is the first time I've tried to spray shellac. It was bullseye, out of the can, and I cut it with denatured alcohol. I sprayed it, and it looked ok at first, but as it dried, it seemed to pucker in spots and give me orange peel. It's acting like I put it on too thick, but when i tried to lay it on thinner, it didn't seem to be atomizing correctly, and it went on a bit spotty. I put it on heavier to make it flow, but then it didn't seem to dry right. What did I do wrong? Not thin enough? What you could be doing wrong could be not spraying the right viscosity for the needle/nozzle combination, to much air pressure, to little air pressure, too much air volume, too little air volume, incorrect fluid flow, needle set too far out from the nozzle, needle set too far into the nozzle, or any combination of the above. This just about covers everything that *could* possibly be wrong, so it really doesn't narrow things down for the OP. If there's orange peel then the only reason for that is a first coat that is too dry followed by wetter coats that the sprayer attempts to flow on. That's what creates the orange peel - subsequent coats bridge the spotty coverage of a dry coat and create the humps we call orange peel. You can't fill enough with additional coats and it will always look worse after it dries than it does when it's wet. Thinning the fluid should be per the manufacturer's spec. It's usually ok to thin a bit more if the gun does not seem to spray it freely, but generally starting with manufacturer's spec is a very safe starting point. Air flow, pressure, etc. are easily adjusted by shooting at a scrap and adjusting to get a good fan and a good coverage. You should easily be able to flow enough to cause a run if you just hold the gun in one place. Spray with a slow, steady pattern, just overlapping each pass. You should imagine that you're stretching a thin film of that clear stuff that wives keep in the kitchen cupboard and that *only* wives can properly stretch over a bowl of leftovers, over your workpiece. One pass on an area. One pass. Not two. Not a little touch up. One pass. End to end. Watch your flow as you're laying it down. You'll see if it's going on too heavy. You want to see it flow on. Let it tack up per the manufacturer's spec between coats. No shortcuts here. Smoke a cigarette, load the woodstove, instruct the wife in the art of changing car tires - whatever is necessary to distract you while you give that coat the required flash time. Then you can put on another coat. Flash times and dry times are going to be affected by temperature and humidity, as well as how thick the coats are. A good wet coat is thicker than a dry coat, but not so thick that you should see protracted dry times. It's not that you're trying to put it on thick, you're trying to put it on wet. Keep that though in your mind. Remember the plastic wrap idea. Most folks make the mistake of spraying too fast as they fear runs. Spray too fast and you get dry coats which result in orange peel. It sands out, so it's not the end of the world, but it is extra work. It's unlikely that even a three pound cut of shellac would need thinning but with the viscosity cup you will at least have an idea of where to start. If you know you have the right viscosity and needle/nozzle combination all you have to do is play with the air volume and fluid flow and needle set. Agreed the viscosity cup can be helpful, but the same can be achieved by spraying at a scrap target and observing the fan. It's all a matter of what makes you comfortable. I wouldn't want the extra step of the viscocity cup, but others may well prefer to go that route. The alternative is playing with all the factors in the rather large number of combinations they present.In other words without at least some fact based info you are just ****ing in the dark. Not really. Again, you have the starting point defined by the manufacturer. Thin to that point and start spraying on a scrap. Adjust the gun and tackle the workpiece. There is no shooting in the dark, ****ing in the dark - (by the way... if you're going to **** in the dark always make sure you know where the electrical outlets are), it's just a simple matter of setting up the gun. That's something you have to do anyway. |
This just about covers everything that *could* possibly be wrong, so it really doesn't narrow things down for the OP. If there's orange peel then the only reason for that is a first coat that is too dry followed by wetter coats that the sprayer attempts to flow on. That's what creates the orange peel - subsequent coats bridge the spotty coverage of a dry coat and create the humps we call orange peel. You can't fill enough with additional coats and it will always look worse after it dries than it does when it's wet. Thanks for that mike. I printed it out, and will get to the bottom of it by trying some of the tests you recommended. It seems like you are right -- it went on too dry at first, and then didn't flow out correctly. It's a panel door that I'm spraying, so it has a lot of nooks and crannies that are hard to get evenly. |
"mark" wrote in message ... This just about covers everything that *could* possibly be wrong, so it really doesn't narrow things down for the OP. If there's orange peel then the only reason for that is a first coat that is too dry followed by wetter coats that the sprayer attempts to flow on. That's what creates the orange peel - subsequent coats bridge the spotty coverage of a dry coat and create the humps we call orange peel. You can't fill enough with additional coats and it will always look worse after it dries than it does when it's wet. Thanks for that mike. I printed it out, and will get to the bottom of it by trying some of the tests you recommended. It seems like you are right -- it went on too dry at first, and then didn't flow out correctly. It's a panel door that I'm spraying, so it has a lot of nooks and crannies that are hard to get evenly. It's like anything else - practice makes perfect. Well... perfect practice makes perfect. I should have mentioned in the my post - and in fact David did mention - watch your distance. Try to stay within 6" of your workpiece. Spray from too far away and the atomized spray goes on dry. Experiment with the direction you point your gun. When you're going down the length of the door you can spray in-to-out a bit so that you get a good coverage on the edge treatment of the panels and the styles and rails. You'll get it - just keep working at it. -- -Mike- |
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http://www.shellac.net/ShellacPricing.html Look for shellac retarder on this page. It may help you with your problem. On Sun, 31 Oct 2004 01:29:27 GMT, "mark" wrote: This is the first time I've tried to spray shellac. It was bullseye, out of the can, and I cut it with denatured alcohol. I sprayed it, and it looked ok at first, but as it dried, it seemed to pucker in spots and give me orange peel. It's acting like I put it on too thick, but when i tried to lay it on thinner, it didn't seem to be atomizing correctly, and it went on a bit spotty. I put it on heavier to make it flow, but then it didn't seem to dry right. What did I do wrong? Not thin enough? |
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