Woodfinishers Weblog

Wood finishing forum for professional finishers

Bubbles in the finish

The following is a problem a follower sent in as a question, while it may be long I thought I should publish the diolog for all to have the benifit of: 

I am posting his question with out contact information for his privacy

 

From: Antonio  
Sent: Sunday, August 23, 2009 7:10 PM
To: info@annexpaint.com
Subject: needing advice and supplier

 

Hey guys,

We are a medium sized kitchen manufacturing firm based in the Bahamas.  Stumbled across your forums while looking for advice in solving some problems we are having which also haves us seeking new suppliers for professional finishing products.  Can you offer some input on the following problem?
For most of our darker Cabinetry finishes we stick with basic MagnaLac finishes, working from oil based stains to lacquer sealers then on to lacquer clear coats and the only problem is the occasional white cloudiness that is a pain in the a** to get out, usually this is when we spray in cooler weather, right now we still spray outdoors and have our drying racks indoors.

Now here is where the problem comes,  for our lighter colored cabinetry we stick with waterborne clear coats (minwax polycrylic) over water based stains with no problem but lately we have been trying to use the same clear coat system over waterbased paint.  For some reason we get constant bubbles.  We do everything by the books,  lacquer based (pratt & lambert) white undercoater, 2 coats of water based (benjamin moore) paint then after 24hrs of drying,,, the clear coat,,, and the BUBBLES!! We thought maybe it was reacting to the lacquer primer underneath so we re-prime with water based primer then final coat but still bubbles!! We use a basic compressor system with a devilbiss siphon gun (1.7mm nozzle). 

I know polycrylic is not exactly pro stuff but being a small island we are veryyy limited to the products we have access to, and would have to spend alot on importing tons of different products to test.  What do you think is causing the constant bubbles?  We spray polycrylic straight out the can.

any input would be appreciated.

AAntonio

Here was my reply:

Hi Antonio,

 Thanks for the data, that’s and interesting one, Bubbles come from a number of things usually it is because it is too hot and the top most layer is drying faster than the bottom of the layer which is still off gassing and so you have a gas trying to come through a layer of almost dry material which then forms a bubble.  The common solutions is to use a retarder or spray when it is not quite as hot. Out here in California there are a number of shops that do there spraying at 4 in the morning.

 You might want to try thinning the material down with what ever the manufacture recommends, sounds like just water will do, the next thing is getting a retarder for the material. I have found that regular Lacquer retarder works well as a retarder for water based products. That however is not a manufacture recommendation and would be something you would want to test first. Best Practice is to use the retarder the manufacturer recommends. As a point when adding a retarder to a water based material you should mix the retarder 50 /50 with water first and then add it to the lacquer. And you would use more than about 4% retarder other wise you are

 The White haziness is a similar thing, Moisture entrapment. As the lacquers is evaporating it is cooling down the surface and condensing the moisture in the air which them is trapped in the coating. You can do a few things for that, again adding retarder, or you can heat your materials i.e., the lacquer or you can move into a climate controlled space (sometimes not possible)

 Another thing that can cause bubbling is air pressure too high on your guns, another is a that you have seal leak on your gun on the fluid side that is letting air in to your fluid mix and frothing it up in the can. That doesn’t sound too likely.

Let me know how that goes and if you can send pictures and I’ll post it.

 If you want me to ship you materials I can do that.

 Greg Saunders
ANNEX PAINT
818-439-9297

August 25, 2009 Posted by | Finishing failures and the fix, polyurethane | 4 Comments

Finishing failures and their fix

This page and category is going to be dedicated to the disasters that we as professional finsihers have all had, seen had to fix, and have heard about. I think the point here is to give others a heads up and possibly avoid  the shoals that various projects have run aground on.  I have found that most failures have come about from not knowing or not understanding  the basics of what you are doing. Too many times I have had “Do it yourselfers” come in with the attitude that there is noting to the business and it simple as pie. Finishers just charge and arm and a leg for nothing. 

It is simple and the fundamentals are fundamental but you have to know them and it does take a certain amount of skill and practice, to add to that, the materials are changing all the time and what preformed one way last year has now been reformulated to be compliant now preforms slightly differently. After a Do it your selfer has had a little trouble and has seen what it really takes to do the job they tell me they would have prefered to have paid a professional. That being said you can learn the trade and it can be rewarding. Just don’t set your self up for a loss by walking into the business arogent and uninformed, thats like a  virgin making an incausious  visit to  a military brothel.  the out come is not going to be pretty. 

I have more things to add to this catagory  but I would be interested in your comments and your failures send pictures if you can and we’ll post a few light houses to save others the disasters that we have had to weather.

Thanks,

Greg Saunders

August 25, 2009 Posted by | Finishing failures and the fix, Uncategorized | Leave a comment