A DIY & home improvement forum. DIYbanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » DIYbanter forum » Do - it - Yourself » Woodworking
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Woodworking (rec.woodworking) Discussion forum covering all aspects of working with wood. All levels of expertise are encouraged to particiapte.

spraying shellac with an hvlp -- bad results



 
 
LinkBack Thread Tools Display Modes
  #1  
Old October 31st 04, 02:29 AM
mark
external usenet poster
 
Posts: n/a
Default 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?


Ads
  #2  
Old October 31st 04, 02:57 AM
cm
external usenet poster
 
Posts: n/a
Default

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?



  #3  
Old October 31st 04, 03:06 AM
Rumpty
external usenet poster
 
Posts: n/a
Default

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?




  #4  
Old October 31st 04, 03:44 AM
mark
external usenet poster
 
Posts: n/a
Default


"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.


  #5  
Old October 31st 04, 11:26 AM
JGS
external usenet poster
 
Posts: n/a
Default

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?


  #6  
Old October 31st 04, 02:43 PM
MikeG
external usenet poster
 
Posts: n/a
Default

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

  #7  
Old October 31st 04, 06:32 PM
David
external usenet poster
 
Posts: n/a
Default

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?


  #8  
Old October 31st 04, 07:10 PM
Rumpty
external usenet poster
 
Posts: n/a
Default

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



  #9  
Old October 31st 04, 11:07 PM
Mike Marlow
external usenet poster
 
Posts: n/a
Default


"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-



  #10  
Old October 31st 04, 11:31 PM
David
external usenet poster
 
Posts: n/a
Default

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.


 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Demystifying Shellac A Dubya Woodworking 2 January 21st 04 10:16 PM


All times are GMT +1. The time now is 02:00 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.SEO by vBSEO ©2010, Crawlability, Inc.
Copyright 2004-2014 DIYbanter.
The comments are property of their posters.