Replies

1. 
   flairwoodworks | Jan 10, 2009 10:50pm | #1

   I don't have any experience with such a task, but it sounds strange to me. Why are you using epoxy? Could you use CA instead? Hot Stuff is much thinner and dries much faster. If you must use epoxy, perhaps you could lay the vessel on its side and only coat one segment at a time before rolling it and repeating.

   Chris @ www.flairwoodwork.spaces.live.com
   (soon to be www.flairwoodworks.com)

    - Success is not the key to happines.  Happiness is the key to success.  If you love what you are doing, you will be successful. - Albert Schweitzer

1. 
   Silverdog | Jan 11, 2009 08:02pm | #4

   Thanks for the responses - further clarification - these are thin wood vessels and the area to be covered is about 2 square feet - spraying is not an option. The finish needs to be high gloss, clear and resistant to water and mild solvents - hence epoxy. Never thought of the silicone contamination issue - yes I do use non-clog sandpaper so will try washing the surface with solvent before coating.

1. 
   john05 | Jan 12, 2009 02:02am | #5

   Hey Silverdog

   You have had some good tips so far, another cause may be the viscosity of the epoxy. If the temp is cold when you apply the epoxy it simply wont flow out you can gently heat in microwave/warm water or a light box only gently though.

   Slow cure is generaly used when the ambient temp is high so if its cold your increasing the problem.

   Rgds

    

   John

2. 
   roc | Jan 11, 2009 06:28am | #2

   It sounds like you have a problem with "surface tension". Same thing that causes water to bead up on a waxed car. No kidding. You may need to do some thing to brake the "surface tension" to allow the fluid to "flowout".

   What you have described is like what finish people call a "fish eye" . One thing that causes this is silicone contamination of the surface. Some sanding paper, the white stuff, has a non-clog treatment that can be problematic in this way.

   Be sure there is nothing involved that could introduce silicone onto the surface. This can cause "fish eyes" which act like your indentations.

   If you have silicone involved on a current piece you may need to swab the vessel out with some solvent. There are specific solvents intended to get rid of problems like the fisheyes but they are for auto body/auto painting. Would probably work fine on the wood but must let the solvent evaporate for many hours. So it does not mess up your epoxy coating.

   One way silicone or other problem causing lubricants can wind up on your surface is blowing your project down with compressed air. The silicone/oils are transmitted from your compressor through the air lines as a mist in the air and onto the surface.

   So don't use compressed air to accelerate the drying if you wash your project with water or solvent.

   One of the glue articles in FWW demonstrated that sanding the surface before gluing broke down the surface tension and allowed the glue to flow out rather than bead up. So sanding may be all you need to do.

   See FWW article called How yellow Glue Works by Chris A. Minick issue Nov/Dec 2003

   I was not able to get this article on line. It is in the "A Closer Look " section in the paper magazine.

   Perhaps washing the surface with soap and water and then rinsing well would be the way to go. I would give this a test on some scrap though. I mention this because when I need to draw on glass with india ink that is how I prepare the glass so the ink behaves like it should. Once the glass is clean ( no surface tension ) the ink will flow off the dip style pen onto the glass and not skip and not bead up.

   Here is an article on fisheye:

   http://www.taunton.com/finewoodworking/SkillsAndTechniques/SkillsAndTechniquesPDF.aspx?id=2920

   Good night and good luck
   roc

   PS: I never considered you may be working with a material other than wood. If metal then solvent, followed by soap and water and dry and Bob's your uncle. Use the coating in a warm environment.

   Edited 1/11/2009 1:15 am by roc

   
   

   ---

   Edited 1/11/2009 1:23 am by roc

3. 
   davcefai | Jan 11, 2009 08:54am | #3

   Assuming that the vessels are metal this may help a little. My experience is in large process vessels and is based on observation and discussions with contractors.

   1. Are they new? If so they need degreasing.
   2. The usual way of applying epoxy to metal vessels is by spraying with in-flight mixing. ie the gun has 2 nozzles and the components are mixed as they leave the gun. Apart from the easier cleanup this allows very rapid setting epoxies to be used.
   3. If the vessels are not stainless steel the usual pretreatment is shot blasting.
   4. Even paying big bucks to specialised contractors you do not end up with a finish like, say, a ceramic bath. The contractor guarantees a minimum thickness but the undulations are always there. The only time I have seen a near-perfect coating is with glass-lined tanks where the tanks are spun on their long axis to evenly distribute the molten glass. Even then there were imperfections which were patched with gold patches.

   Now you know why I always demand stainless steel :-)

4. 
   AlanWS | Jan 12, 2009 05:15am | #6

   It could be surface contamination, or it could simply be that the viscosity is too high. If that's the problem, warming it gently with a heat gun could help it flow better. But don't heat it too much or it will cure too fast, heating up even more.

   If it's contamination, the best solution is to avoid contaminating it, rather than trying to clean it off after the fact. Use scrap to check whether your problem could be stearated sandpaper, tack cloths, or something else you use. Light sanding might work better than solvent to clean the surface.

   Rather than mirror coat, you might do better with system three clear coat. That stuff is very thin and slow curing. It soaks in well to waterproof things, but looks more like a decent wood finish, and less like you have encapsulated the wood in plastic.

5. 
   Quickstep | Jan 12, 2009 06:03am | #7

   I know you said it's not bubbles, but...... I've discovered something when using epoxy as a coating. As the epoxy gets absorbed by the pores (especially in ring porous woods), the air it displaces rises to the surface and forms a bubble that pops, leaving a small crater if the epoxy has begun to kick a little and can't level out quickly enough.

6. 
   yamslobber | Jan 12, 2009 08:47pm | #8

   A few rules to live by with epoxy:

   Never use tack cloths. Never use acetone to clean either. Use Denatured Alcohol, with a brand new clean cotton cloth. After cleaning, try not to touch with your fingers, as it may contaminate the surface.

   Always stir the pot longer than you think you need to. I like to alternate pumps from resin and hardener so it is already mixed a little. Then I will stir with a very clean (wiped with DNA) paint stick for at least three minutes. Stir very slowly, and wipe the edges of the pot to get all the material integrated.

   Never use foam brushes. A cheap bristle brush is best. I like to beat the heck out of the brush on a table to loosen any bristles that are going to fall off onto your perfect finish, and be discovered when its too late.

   You can thin out your mix with DNA for better flow out. But the best stuff to use is "Additive F" which is available from Resin Research. It gets added to the hardener in very specific quantities. I recommend doing lots of research on thinning epoxy if that is the route you want to take, as it is a whole article by itself.

   Never keep going back over the coating with your brush. Once you get it brushed on, let it flow out on its own. The more you brush over it, the more you risk getting air bubbles. Brush very slowly once a direction, then perpendicular to that direction. Then stop.

   The System Three is a pretty good product, but I have had better luck with Resin Research. Also, it sounds like you may be able to go to a fast hardener. When you use a slow hardener, it often tends to run out too long, and be more prone to bubbles and pooling. Slow hardeners are normally reserved for doing multi layer glass lay-ups, where more time is needed.

1. 
   Silverdog | Jan 14, 2009 04:23am | #9

   Thanks for the good advice. I looked at Resin Research products but was confused by all the combinations of resins and hardners - System Three Mirror Coat looked like the simple answer - perhaps not. Any recommendations on combinations of Resin Research resin and hardners? Could I speed up curing of System Three Mirror Coat? Presumably adding more hardner is not the answer.

1. 
   yamslobber | Jan 15, 2009 07:42am | #10

   Correct, more hardener will not do. They have these mixtures so dialed in now, you have to do them exactly as they give them to you. I have not used the Mirror Coat, but I have used a similar product from MAS epoxy. I think you will find they all give about the same amount of shine, especially by the second coat. With Resin Research, I use the 2000 Epoxy, with the 2100F hardener (fast hardener) One good place to order it is from Foam EZ, its a surfboard supply company. They have some pre-packaged kits with the epox, hardener, and additive F. All RR stuff mixes at a two to one ratio.Another thing you should know about fast hardeners is they are more susceptible to UV light, and they will turn yellow a couple of years if they are in sunlight. If this is not an effect that you want, you can use a Spar Varnish with a UV blocker as your final coat. (usually sold as marine spar varnish) This will help keep the epoxy clear for years to come.

1. 
   Silverdog | Jan 16, 2009 04:40am | #11

   Thanks for the good advice.