I need help to learn how to make perfect vernish on our veneered honeycomb panels

[teakcell]

Hi, I need advices on how to varnish as well as possible on furnitures. We glue our veneer on peeling to make cold moulded furnitures.
The veneer is glued with epoxy and the glue goes through the veneer because we vaccum. So we use the same epoxy as a wood filler. Then sand paper and lay pu varnish on top sealer and top coat. We have poor results untill now. I need help. Thank you in advance. Laurent

[KnottyBuoyz]

I suspect the epoxy bleeding through the veneer under vacuum is the problem with the finished product. You might want to look for other adhesives more suited to the process. There's some good info on the www.joewoodworker.com web site on veneers and which adhesives to use with each type.

http://www.joewoodworker.com/veneering/why-use-veneer.htm

[teakcell]

Thank you but I want to keep on using epoxy to glue our veneer for strength reasons.

[apex1]

Thank you but I want to keep on using epoxy to glue our veneer for strength reasons.

Leave it to saturate even!
If that does´nt happen, feed more resin!
The prob is not the resin shining through!!! It is the partially dry surface! giving a different pattern.
Anyway, cover the outside with one (better two) additional layers of very liquid resin. DO NOT USE THINNERS AS MENTIONED SOMEWHERE!!! Sand down to all white surface, thats almost close to veneer. Cover with another layer resin. Sand down to all white, not to veneer. Apply 15 to 25 layers pu. First layer is not sanded! every following just gentle! Last one has to show ALL WHITE again!!! before final spray is applied!!!
Have a nice, clean shave using that surface!

And BTW. building a boat in Burma.... chapeau !
During August 2009 I´ll come to Mandalay again,maybe we meet?


Regards
Richard

[Landlubber]

teak cell,

When varnishing the trick is to fill the grain. Apply your varnish first coat thinned out 50%. This will allow penetration through the wood. Allow to dry then top coat with straight varnish, you can thin it a bit (5-10%) if you feel that the product is too thick for application. Allow two to three coats, then sand back till flat, but never sand back to the wood. If the wood shows, stop sanding and apply a few more coats, allowing to dry. Apply about 5 to 7 coats all up.
Once you have the surface completely filling the grain, you can prepare for the top coat. Sand the final surface with 240 grit paper (320 if you feel the need, but 240 is fine), final sanding with the grain so the scratches from the paper do not show. Wipe down with a clean cotton rag such as sheeting or old T shirt. Wipe down till there is no dust, then get a tack cloth from a crash repairer. A tack cloth is a waxy muslin cloth folded into a small square. Open it out fully and very lightly wipe the surface for the final time. Apply the varnish carefully over this prepared surface and the result will be a mirrored finish.
When dipping the brush into the varnish, NEVER wipe the side of the brush on the can of varnish as this just drips shit back int the can and polutes the quality. Just dip the hairs in and gently remove, the technique becomes quite natural after a while, and the product remains pure.

I have been to Burma, and doubt that you can buy a tack cloth anywhere, but try the car repair yards, there may be one there that does quality work, they will surely have them.
If it proves impossible I will post you some.Just contact me.

Kind regards, Landlubber

[teakcell]

thank you well noted. I need to keep on using epoxy for the veneer.

[teakcell]

Thanks. I will revert when the tests are finish.

[robherc]

Maybe varnishing the outside of your veneer BEFORE infusing the part would help? This would eliminate the possibility of epoxy bleed-through harming the varnish....I'm not sure about the possibility of getting epoxy over top of the varnish though, so it might not work out as well as I'd hope.

Just a thought

[teakcell]

Nice thought. Thank you. We already tested and it bleeds on the joints.

[teakcell]

Nice thought. Thank you. We already tested and it still bleeds on the joints.

[teakcell]

I appreciate you all for kind help and assistance. My results, I shoud rather say my temporary conclusions are:
- epoxy can be mixed with xylene without a problem as it is a non active charge: it makes the epoxy layer easy to lay. If not, you need to buy special stuff that I cannot find here.
- Ep + pu bond very well together.
So after 2 layers of epoxy, lay your pu with the proper gun (need to ask a specialist who will tell you wich gune hole diameter to use). THis might be the most important for us.
Ly as many PU layers as you need remembering that the more solvant, the more layers, the less the vernish, the higher the price.
We are studying trying with brush or cotton cloth but we can afford because labor is cheap over here. If I were in EU, I would go for airmix solution ...
The path to ''varnish mirror'', the real one, is a long path that we are trying to reach.

[robherc]

Hmm, just a thought, I've found that my urethane coats work best (fewest # of bubbles/dry spots per coat) when I apply them with an el-cheapo foam brush (the wider the better), or with a spray-gun (HVLP is ok, but airless is best). If labor is cheap, go with the foam brushes I'd say.

Also, (and I'm guessing you already know this part) you can MUCH more easily get "varnish mirror" if you do all of your varnishing in a "clean room" with lots of air filtration and NO DUST. I'm working on building a bigger, cleaner room for my projects, because I don't currently have efficient enough filtration; thus, I'm still getting (very) slight surface flaws (granular bumps) in my varnishes.

[teakcell]

Can you tell me why el-cheapo brand is better. Would you its basic characteristics? Do you have any pictures if the best way you use it? I won't find that brand here and will try with a piece of foam from mattress or sponge and see.
Could you tell me what is the difference between HVLP gun and others.
Do you use foam brush for the last coat too ?
Room is extremely important and we are working on it. We are testing a simple systeme where the room is elevated from the ground (3-4 m) and the air and dust can come out easily. I tried in a 40' container with pressurized air (we just blow a lot of air from the top and it goes out from the holes at the base of the container) with 50% success. We are aiming better so we try a new system. I will keep you informed if interested. Please tell me how you do.

[PAR]

There's no way to avoid your bleed through with your method. I just did a veneer deck, using .125" veneers and vacuum bagged them down. Same issue, but I expected it. Top coat the veneers with at least two coats of unthickened epoxy, preferably one formulated to be especially clear. As mentioned, you'll want to "level" each coat with 220, progressing to 320 grit, using a long board on large surfaces. Wet the surface to check for smoothness. If it's not apply more epoxy or use the first few finish coats to complete the leveling process.

Once satisfied with the "smoothness" of the surface, move on to "bulking up" the finish coating. Basically you want apply successive finish coats, building up thickness and removing minor surface imperfections as you go. Eventually you'll need to apply a top coat. This is the actual finish you'll see and should be applied as neatly and cleanly as possible.

In fact, the neatness of the result is mostly related to the environment you're working in. The preferred choice for a finsih booth is down draft, where the air comes in from the side and is exhausted through the floor. Of course the air should be well filtered, not a huge volume, just enough to change out the air reasonably quickly without drafts or blowing up dust. It should be able to handle over spray promptly.

You can dilute epoxy with xylene, but it dramatically weakens the molecular bonds within the epoxy. Adding solvent to epoxy isn't a good idea, unless you have a very comprehensive understanding of the chemistry involved. If you need to change the viscosity of epoxy, you should work at higher temperatures.

The way I see you project(s) is four fold: bonding the veneer to the substrate, which you seem to have well in hand, secondly leveling the surface so a finish can be applied, third supplying sufficient bulk of base finish and lastly getting a smooth, glass like result from a top coat.

Conditions will dictate the quality of the top coat, assuming you've applied the material properly. If you don't have truly clean conditions, you'll get dust. Florescent lights create dust, so use a different type of light. It also helps to have the lights at the side of the booth, rather then over head, so you can see imperfections better. Environment control is the only way to get good top coat results.

Bulking finish coats can be done in moderately clean environments, though you'll have more work to do, "cleaning up" the separate coats of material.

Getting the veneers smooth with epoxy, takes practice, just like a good automotive body man needs to prefect his craft. With the right tools and practice, leveling epoxy isn't especially hard, but it is tedious and requires a fair amount of skill.

[teakcell]

With wich tools do you apply epoxy and pu varnish? What temperature do you advise to cahnge the viscosity of ep? Are you sure that xylene does weakens the epoxy as it is supposed to be only a vector of the epoxy: it is supposed to go away when drying. IN my chemistry books, xylene is listed as non active charge.

[robherc]

The "el-cheapo" foam brushes I was referring to were not a specific brand name. I was using "el-cheapo" to refer to any cheap foam brush that you can pick up at a discount store. The ones I use cost me about $3 for a package of 10 brushes.
As far as technique goes, I dip just the tip of the angled part of the foam 1-2mm into the varnish (I like spar urethane...good all-weather varnish, but it's not especially cheap) then smooth it onto the surface. Each dip covers about 7-15cm of surface, the same width as the brush, depending on how much urethane soaked into the foam. It's a VERY labor-intensive process, but it yields a good, high-gloss finish coat for me.

A HVLP (High-Volume Low-Pressure) sprays more media (varnish) with less air pressure than a "conventional" air spray gun. I'd still highly recommend an airless spray gun for varnish though, as most HVLP and "standard-pressure" air spray-guns require you to thin your paint/varnish, and this won't help smooth your finish coat much...although it WILL make the process require more coats to get to the same build thickness.

[apex1]

You can dilute epoxy with xylene, but it dramatically weakens the molecular bonds within the epoxy. Adding solvent to epoxy isn't a good idea, unless you have a very comprehensive understanding of the chemistry involved. If you need to change the viscosity of epoxy, you should work at higher temperatures.



As usual I widely agree with your recommendations, but here is a possible solution to control viscosity by adding a diluent based on epoxypropoxy.
That does not weaken the crosssections too much because it is a ACTIVE diluent. For cabinetry it should be fine anyway, I would not recommend in applications with highly induced stress.
http://www.ezentrumbilder.de/rg/pdf/si_en_Active_diluent_EPD_BD.pdf
and:
http://shop.ezentrum.de/4DCGI/ezshop?hid=27&sprachnr=2

best regards
Richard

[PAR]

Richard, I didn't see anything on that site that was a diluent. Can you provide a direct link to the specific product?

Teakcell, most of the chemicals typically used to thin epoxy, will alter the physical properties of the cured epoxy. Most affect the molecular crosslinking that takes place, by working against a complete 3 dimensional link or physically presenting certain percentages of 2 dimensional linkage from occurring. In all cases, this lose of linkage will weaken the epoxy. In defense of this "thinned" epoxy debate, there are times when you may want to change the physical properties of the cured matrix and specific chemical dilution can provide a means toward this. Preforming this with predictable results can be a tedious and drawn out process of testing and re-testing. I personally have a few different mixtures that I use regularly, in application specific roles. They've been repeatedly tested and now have stood the test of a couple of decades in service, so I can predict their performance accurately. None of my special mixtures are used in any finishing applications.

[teakcell]

Can you be more specific with the mixture that you use? You said that ep can be liquid when heat. Which temperature do you advise and which tools do you recommend to apply the ep and pu ?

[teakcell]

Would anyone knows where to find plans or drawing, explanations on how to make a proper painting room? Which air temperature do wee need, air flow in and out ...

[robherc]

Hmmm, just a thought...

Why not simply use a lower-viscosity epoxy? Depending on the finished properties you're looking for, there are some excellent epoxies out there with viscosities that go down to below 500cps...some are even thinner than most varnish. surely any of those would work very well for a surface-coat epoxy to fully saturate your veneer prior to varnishing. Some of them (heat-cured) even have pretty favorable hardness, strength, and heat-deflection properties, good enough for usage in (some) structural laminates.

[teakcell]

Good idea but I have troubles finding more than one supplier here! We have have one type of glue. I can always import and stock but I try to avoid that as I have enough stock.

[robherc]

Would anyone knows where to find plans or drawing, explanations on how to make a proper painting room? Which air temperature do wee need, air flow in and out ...

I'd recommend doing a patent search for "paint spray room" with Google at http://www.google.com/patents . Any patent that's over 7 years old is considered "expired" and can be used by anyone.

[apex1]

Richard, I didn't see anything on that site that was a diluent. Can you provide a direct link to the specific product?

.

PAR
unfortunately not possible, but:
http://www.r-g.de/
change language..... left side bottom
goto E-shop.........click......Epoxy resins....click.......EP additives ..aahhh
see them all ... be jealous....... bloody Huns:D

With pleasure
Richard

[teakcell]

I'd recommend doing a patent search for "paint spray room" with Google at http://www.google.com/patents . Any patent that's over 7 years old is considered "expired" and can be used by anyone.
well thought. Thank you

[apex1]

Would anyone knows where to find plans or drawing, explanations on how to make a proper painting room? Which air temperature do wee need, air flow in and out ...

Laurent,
might be worth to ask one of these guys ? PM?

http://www.boatdesign.net/forums/fiberglass-composite-boat-building/awlgrip-knowledge-challenge-20793.html

Regards
Richard

[Kaptin-Jer]

I don't know the availability where you are, but I have been using paperbacked veneer and I have not had any bleed through. I am not vacuum bagging only rolling with a laminate roller, low tech but it has been working well.

[apex1]

I don't know the availability where you are, but I have been using paperbacked veneer and I have not had any bleed through. I am not vacuum bagging only rolling with a laminate roller, low tech but it has been working well.

Kaptain
He is in Burma, almost nothing available there. And his problem might be that he uses Teak (oily), but he must use Teak.

Regards
Richard

[teakcell]

I don't know the availability where you are, but I have been using paperbacked veneer and I have not had any bleed through. I am not vacuum bagging only rolling with a laminate roller, low tech but it has been working well.

Yes, good idea too. I don't really have trouble with Ep going through the veneer and I would even say that I like that because it cannot be better bonded. My problem comes after applying another layer of ep and additionnal Pu varnish in order to reach a top mirror quality varnish. I have only one kind of epoxy available in the local market. I can always import but it is a real trouble here. So, as long as I can do with available products, I will try.

[teakcell]

I did. Thanks

[apex1]

I did. Thanks
Laurent,
my guys here ask me "why is he using Xylene?" "If the bonding resin bleeds through, evenly distributed, just add two more layers (green) and the race is ran" Why Xylene?
Regards
Richard

[PAR]

Xylene isn't a bad choice, especially if you want to increase the flexibility of the cured goo. At the right temperature, it can also increase penetration, of course with the knowledge it will reduce strength and water proofness of the cured coating.

I know what you're going through Teakcell. Those seams will suck up resin like a sponge. My technique was to apply a few coats to the seams only, to fill them, knocking down the over flow after each run. It's a pain, but the only way to level the seams with the curved veneer surface I was working with.

Another option would be to "flood" coat the surface. This is much like how a table top is done. You literally pour on the epoxy and let it pool. I use a 1/16" notched spreader to move it around the surface, which self levels if the viscosity is correct and the resin has enough time to flow out before it kicks off.

For panel work, I would think flood coating is the way to go.

[apex1]

Xylene isn't a bad choice, especially if you want to increase the flexibility of the cured goo. At the right temperature, it can also increase penetration, of course with the knowledge it will reduce strength and water proofness of the cured coating.
Thank you PAR

Another option would be to "flood" coat the surface. This is much like how a table top is done. You literally pour on the epoxy and let it pool. I use a 1/16" notched spreader to move it around the surface, which self levels if the viscosity is correct and the resin has enough time to flow out before it kicks off.

For panel work, I would think flood coating is the way to go.

To this point my first reply should lead (post#4)! Feed more resin.

Regards
Richard

[robherc]

Yes, good idea too. I don't really have trouble with Ep going through the veneer and I would even say that I like that because it cannot be better bonded. My problem comes after applying another layer of ep and additionnal Pu varnish ...
Here's a thought (possibly useless, maybe not) that just hit me:
Why not saturate the veneer with epoxy first? That way there will be no bleed through (though, if done right, the cured bond should be as good), and there will be no "dry spots"...just evenly epoxy-soaked wood. You could probably even VIP (with flow media, of course) or vac-bag the veneer when you do this to keep from gaining too much weight from over-applying the epoxy, if weight is critical for you.

[robherc]

To All:
In another thread, teakcell told me he uses veneer over honeycomb. If that's the case in this thread too, then I think we're talking "weight-critical" applications, and feeding more resin into the vacuum might just rapidly increase weight by filling the honeycomb with epoxy. If that's not the case here, then "feed more resin" could be exactly what the doctor (Dr. Richard?) ordered.

[apex1]

I think we're talking "weight-critical" applications, and feeding more resin into the vacuum might just rapidly increase weight by filling the honeycomb with epoxy. If that's not the case here, then "feed more resin" could be exactly what the doctor (Dr. Richard?) ordered.

Rob
you are right, we are talking "weight-critical" applications. But the honeycomb cells are already covered by plywood to which teakcell will apply the veneer.
So I do´nt see a real prob feeding a spoon of additional resin.
Regards
Richard

[robherc]

OK, I guess you have more info than I do on this one...if he has already applied plywood to the honeycomb, then yes, I would say feeding a little more epoxy would prob. be the easiest way to fix the problem...do the same thing as a pre-preg. veneer, but without the extra step.