Advice on doing a 2Pac Finish

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Originally Posted by Tegmark

I don't know for sure about silicone based products, I use meguiars M105 & M205 & they worked well on oil based. I will try 2pac once it fully cures. I beat it will come up mirror gloss like an auto paint job.

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I got half way through responding to this and then lost the images I had to post up.

Silicone based products and ptfe spray lubricants can cause problems with paint as they interfere with adhesion and create orange peel and other similar issues, including pinholes. Just to be helpful, you don't even have to use these products on the job, or have any direct contact from contaminated tools - having an open container in the same room can cause problems. So, if you are getting seemingly random problems and you have prep'd appropriately then keep this in mind.

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Originally Posted by SPF

Interesting - thanks for posting that up. I have never got enough film thickness for that to happen with 7008. But it happens with just about all common 2 part resins. It is from a combination of the surface tension of the resin plus volumetric shrinkage due to the peak in temperature while the resin thermosets.

If you leave an amount of 7008 in a jar and let it set, you will notice that the resin will appear to climb up the sides of the jar, and once the temperature peaks, and it starts to cool and harden, the resin will pull away from the edges of the jar as it shrinks. The force that this generates can be a real problem with unsupported veneers or thin material if only painted/applied on one side.

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Thanks SPF, good to know that from now on. Back to experimenting.
:)

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Originally Posted by SPF

I got half way through responding to this and then lost the images I had to post up.

Silicone based products and ptfe spray lubricants can cause problems with paint as they interfere with adhesion and create orange peel and other similar issues, including pinholes. Just to be helpful, you don't even have to use these products on the job, or have any direct contact from contaminated tools - having an open container in the same room can cause problems. So, if you are getting seemingly random problems and you have prep'd appropriately then keep this in mind.

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These pinholes are I think from air dissolved in the clear from the bristles working the clear, not that it matters in many cases as when thick the sides bulge up ruining any chance of an off the brush perfect finish.

if I recall 7008 is designed to go on with a relatively thin wet film. The bulges yiu describe sound like a surface tension effect that might go away if the edges of your piece are "broken" or rounded

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Originally Posted by Tegmark

Thanks SPF, good to know that from now on. Back to experimenting.
:)

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Tegmark how did you go sanding and polishing the 7008? The 7008 is pretty good straight off the brush for clarity and shine, but I haven't tried polishing it. I'm keen to see your results, especially if you are doing a broad flat surface.

I'm looking at making a large American oak table in the next couple of months, and am considering either the epoxy and marine PU, or the 7008. I'd like to spray it for even finish, but if the 7008 can be polished, then that would be a quicker and simpler solution.

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Originally Posted by ian

if I recall 7008 is designed to go on with a relatively thin wet film. The bulges yiu describe sound like a surface tension effect that might go away if the edges of your piece are "broken" or rounded

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I tried to brush a coat of 7008 straight out of the can as thin as I could (any thinner & it's hard to apply as its dry & doesn't spread easy). Yet this problem still happens. My guess 2pack was never really good on a brush & its mainly for floorboards etc.

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Originally Posted by SPF

Tegmark how did you go sanding and polishing the 7008? The 7008 is pretty good straight off the brush for clarity and shine, but I haven't tried polishing it. I'm keen to see your results, especially if you are doing a broad flat surface.

I'm looking at making a large American oak table in the next couple of months, and am considering either the epoxy and marine PU, or the 7008. I'd like to spray it for even finish, but if the 7008 can be polished, then that would be a quicker and simpler solution.

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Hi SPF,

Just waiting for a week or two more so it really hardens up, as I applied the coats pretty thick. So far I just finished sanding from 400 all up to 2000 through the grits. Seems easy enough as long as new paper is used.

When I polish, Ill post my results. I intend to do a full hand polish & machine. If it's anything like oil based, it should come up very glossy but look more plastic/opaque on certain angles.

Does anyone know if you can 2pack PolyU over water based wood filler? I tried a test piece & it's been a week or more & no issues so far.

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Originally Posted by Tegmark

I tried to brush a coat of 7008 straight out of the can as thin as I could (any thinner & it's hard to apply as its dry & doesn't spread easy). Yet this problem still happens. My guess 2 pack was never really good on a brush & its mainly for floorboards etc.

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from the Estapol 7008 Technical data sheet

recommended Wet Film thickness 85 microns ( = 0.085 mm)
recommended Dry Film thickness 38 microns ( = 0.038 mm)


Data sheet http://lpb-dev.azurewebsites.net/Upl...pol%207008.pdf

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Originally Posted by Tegmark

Does anyone know if you can 2pack PolyU over water based wood filler? I tried a test piece & it's been a week or more & no issues so far.

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I have a danish couch frame that I used water based filler on with 7008 over the top. This was done 6 years ago and no problems (except the filler lightened over time and is now obvious).

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Originally Posted by Tegmark

When I polish, Ill post my results. I intend to do a full hand polish & machine. If it's anything like oil based, it should come up very glossy but look more plastic/opaque on certain angles.

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I look forward to seeing the results.

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Originally Posted by ian

from the Estapol 7008 Technical data sheet

recommended Wet Film thickness 85 microns ( = 0.085 mm)
recommended Dry Film thickness 38 microns ( = 0.038 mm)


Data sheet http://lpb-dev.azurewebsites.net/Upl...pol%207008.pdf

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These tech specs are for generic floor boards & not a fine furniture application. Any thickness & the problem happens. As far as I can tell 2pack is only good for spraying.

The recommended wet film thickness for Estapol water based Xtra clear is 83 microns, which is near enough the same as for 7008.
and that for Estapol Moisture Cure Polyurethane High Gloss is 100 microns, which is much thicker.
So I'm wondering if you are applying too thick a coat of 7008 which is leading to your problems.


It might be worth a call or email to Wattyl's technical help line

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Originally Posted by ian

The recommended wet film thickness for Estapol water based Xtra clear is 83 microns, which is near enough the same as for 7008.
and that for Estapol Moisture Cure Polyurethane High Gloss is 100 microns, which is much thicker.
So I'm wondering if you are applying too thick a coat of 7008 which is leading to your problems.


It might be worth a call or email to Wattyl's technical help line

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Thanks ian.

I wan't to first try applying coats that are thinned. So I wan't to ask what is the recommended thinning %? 10%, 15%?

I'm going to try 10-15% to see how I go with this problem.

thanks

7008's technical data sheet, suggests 10% as the upper limit for thinning.

also, how cold is it where you are working? Could low temperature be an issue.

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Originally Posted by Tegmark

These tech specs are for generic floor boards & not a fine furniture application. Any thickness & the problem happens. As far as I can tell 2pack is only good for spraying.

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CAUTION

The safety data for Estapol 7008 specifically says -- "Do not apply this product using spray equipment."

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Originally Posted by ian

CAUTION

The safety data for Estapol 7008 specifically says -- "Do not apply this product using spray equipment."

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Many 2pac products need to be sprayed with a grounded gun, and need to have adequate fan forced ventilation - given the purpose of 7008 (floors and timber more generally) it makes more sense to say that it shouldn't be sprayed.

It may also suffer from other problems, but explosion hazard is a good enough reason not to spray it.

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Originally Posted by ian

7008's technical data sheet, suggests 10% as the upper limit for thinning.

also, how cold is it where you are working? Could low temperature be an issue.

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I doubt it. I have applied in a broad range of temp. I get the same results even at 12 degrees C as I do near 30C.

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Originally Posted by SPF

Many 2pac products need to be sprayed with a grounded gun, and need to have adequate fan forced ventilation - given the purpose of 7008 (floors and timber more generally) it makes more sense to say that it shouldn't be sprayed.

It may also suffer from other problems, but explosion hazard is a good enough reason not to spray it.

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As I understand there isn't much difference between 7008 to 2pack polyu in the auto trade. I bet it could be thinned down & sprayed no problems with a good setup. If there is explosive risk with spraying, it would be the same for diy spray painters in their garage id imagine.

What do you guys use for filling deep cracks when you wan't it see thru? I tried to use some 2pack clear, but I get occasional air bubbles stuck in the voids & it takes many coats to fill the cracks as it tends to rise up out of the cracks onto the wood surface.

I'm reading about sellys araldite epoxy glue. Might try that & hope its as transparent as my clear method.

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Originally Posted by Tegmark

As I understand there isn't much difference between 7008 to 2pack polyu in the auto trade. I bet it could be thinned down & sprayed no problems with a good setup. If there is explosive risk with spraying, it would be the same for diy spray painters in their garage id imagine.

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Tegmark

I really think you should read the MSDS for 7008. Perhaps the reason Valspar say "don't spray" is that one of 7008's components or atomised 7008 is a carcinogen?

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Originally Posted by ian

Tegmark

I really think you should read the MSDS for 7008. Perhaps the reason Valspar say "don't spray" is that one of 7008's components or atomised 7008 is a carcinogen?

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Your assuming I haven't read it. I'm aware of the carcinogen threat. I have a respirator, googles for doing it by brush in a unopened area. And if I was ever gonna spray it, I would have a setup like a spray painters garage.

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Originally Posted by Tegmark

I'm reading about sellys araldite epoxy glue. Might try that & hope its as transparent as my clear method.

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I've had mixed results doing this. The worst being when I put it in a crack with a charred edge and the glue dripped over the high points and formed air gaps that were lighter than the char, which looked terrible. The best being when I used acetone to clean the area first with a ground down toothbrush (only one bristle tree wide) and once dry and vented, I overfilled the gap substantially and then vibrated it with a orbital sander until the glue gelled (5 - 10 mins). The trick with this is letting the glue set for the stated time so that it fully cures and shrinks before you cut it back and sand it. As with all epoxy it is still pretty gummy under the sand paper though. If you want it clear, get the ultra clear product.

I've also used epoxy resin and araldite with wood flour to make a filler paste. My tip for this is to use a very sharp blade to trim it down within about 30 minutes of setting. Otherwise it is too hard to cut down without damaging the surrounding area.

I hope that saves you some time and sanding.

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Originally Posted by SPF

If you want it clear, get the ultra clear product.

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Araldite® Ultra Clear | Selleys Australia

Quote:

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Originally Posted by SPF

I've had mixed results doing this. The worst being when I put it in a crack with a charred edge and the glue dripped over the high points and formed air gaps that were lighter than the char, which looked terrible. The best being when I used acetone to clean the area first with a ground down toothbrush (only one bristle tree wide) and once dry and vented, I overfilled the gap substantially and then vibrated it with a orbital sander until the glue gelled (5 - 10 mins). The trick with this is letting the glue set for the stated time so that it fully cures and shrinks before you cut it back and sand it. As with all epoxy it is still pretty gummy under the sand paper though. If you want it clear, get the ultra clear product.

I've also used epoxy resin and araldite with wood flour to make a filler paste. My tip for this is to use a very sharp blade to trim it down within about 30 minutes of setting. Otherwise it is too hard to cut down without damaging the surrounding area.

I hope that saves you some time and sanding.

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Thanks SPF.

I'm trying epoxy now, and its difficult but quick compared to filling up the gaps with the clear it self which takes many fills. But I think the clear is more see thru. I read about the brand Artresin is one epoxy that doesn't yellow over time, so ill try it when I can.

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Originally Posted by Tegmark

Thanks SPF.

I'm trying epoxy now, and its difficult but quick compared to filling up the gaps with the clear it self which takes many fills. But I think the clear is more see thru. I read about the brand Artresin is one epoxy that doesn't yellow over time, so ill try it when I can.

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The other thing that I have been meaning to try for years is optically clear casting resin. Here are some examples:
Polyurethane Casting Resins | Dalchem
Easycast Clear Resin

There are also equivalent epoxies:
Solid Solutions - Casting Resins

These products are used for potting electronics, making castings, and filling behind glass for some specific applications. As with acrylic resins, they can suffer from air bubbles rising up through them if you have not wet the substrate they are poured into and over.

All told, these will be expensive ways to get the clear fill, but once you have worked out the way to use them, they will be bullet proof. If you decide to try any of them I'd like to see your results. I've used these for casting and electronics, but not on timber.

Quote:

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Originally Posted by Tegmark

Thanks SPF.

I'm trying epoxy now, and its difficult but quick compared to filling up the gaps with the clear it self which takes many fills. But I think the clear is more see thru. I read about the brand Artresin is one epoxy that doesn't yellow over time, so ill try it when I can.

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The other thing that I have been meaning to try for years is optically clear casting resin. Here are some examples:
Polyurethane Casting Resins | Dalchem
Easycast Clear Resin

There are also equivalent epoxies:
Solid Solutions - Casting Resins

These products are used for potting electronics, making castings, and filling behind glass for some specific applications. As with acrylic resins, they can suffer from air bubbles rising up through them if you have not wet the substrate they are poured into and over.

All told, these will be expensive ways to get the clear fill, but once you have worked out the way to use them, they will be bullet proof. If you decide to try any of them I'd like to see your results. I've used these for casting and electronics, but not on timber.

Quote:

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Originally Posted by SPF

The other thing that I have been meaning to try for years is optically clear casting resin. Here are some examples:
Polyurethane Casting Resins | Dalchem
Easycast Clear Resin

There are also equivalent epoxies:
Solid Solutions - Casting Resins

These products are used for potting electronics, making castings, and filling behind glass for some specific applications. As with acrylic resins, they can suffer from air bubbles rising up through them if you have not wet the substrate they are poured into and over.

All told, these will be expensive ways to get the clear fill, but once you have worked out the way to use them, they will be bullet proof. If you decide to try any of them I'd like to see your results. I've used these for casting and electronics, but not on timber.

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Thanks. I tried epoxy resin & it was not good tbh. It always creates small air bubbles & is very hard to sand. Not as clear & see thru as the poly clear itself.

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Originally Posted by Tegmark

Thanks. I tried epoxy resin & it was not good tbh. It always creates small air bubbles & is very hard to sand. Not as clear & see thru as the poly clear itself.

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If you are going to use Epoxy, sanding it back is horrible, its gummy when its not fully cured and very tough when it is. If you understand how much it will shrink in a given situation, the better option is to overfill it let it start to gel and then trim it back with a very sharp blade as far as you can. To set your trim height, you can use tape for cutting it back to within 0.15 - 0.25 mm or paper or card tacked down for anything thicker. You simply put the tape down along two edges and run the blade through the glue while the elevation is set bythe tape.

A cheap easy blade to use for this is a disposable box cutter blade glued onto a piece of timber to ensure it stays flat. Make sure the blade sits out at least 4 mm from the leading edge of the timber.

If you want a more permanent solution, you can also modify a plane (good reuse of a cheapy) or spoke shave to do this job. Or you can clamp a plane between two blocks of timber, with the plane set the correct elevation above the glue. If you are going to try a plane for this job, make sure you lubricate the blade so that it doesn't jam as you try to trim the glue back. Use a lubricant that can be easily cleaned off the glue (and timber) later. I use paraffin wax rubbed onto the blade as it lubricates the blade but generally doesn't get onto the parent material.

The other thing to mention is that pushing any blade through epoxy perpendicular to travel is difficult. If you have an approach angle of 35-50 degrees, I find that works well. You may still have to use a slight sawing action but it should take almost no effort.

I hope that helps.

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Originally Posted by SPF

If you are going to use Epoxy, sanding it back is horrible, its gummy when its not fully cured and very tough when it is. If you understand how much it will shrink in a given situation, the better option is to overfill it let it start to gel and then trim it back with a very sharp blade as far as you can. To set your trim height, you can use tape for cutting it back to within 0.15 - 0.25 mm or paper or card tacked down for anything thicker. You simply put the tape down along two edges and run the blade through the glue while the elevation is set bythe tape.

A cheap easy blade to use for this is a disposable box cutter blade glued onto a piece of timber to ensure it stays flat. Make sure the blade sits out at least 4 mm from the leading edge of the timber.

If you want a more permanent solution, you can also modify a plane (good reuse of a cheapy) or spoke shave to do this job. Or you can clamp a plane between two blocks of timber, with the plane set the correct elevation above the glue. If you are going to try a plane for this job, make sure you lubricate the blade so that it doesn't jam as you try to trim the glue back. Use a lubricant that can be easily cleaned off the glue (and timber) later. I use paraffin wax rubbed onto the blade as it lubricates the blade but generally doesn't get onto the parent material.

The other thing to mention is that pushing any blade through epoxy perpendicular to travel is difficult. If you have an approach angle of 35-50 degrees, I find that works well. You may still have to use a slight sawing action but it should take almost no effort.

I hope that helps.

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Thanks good info there. I will experiment. In the meantime while I wait for some stuff to arrive I thought about my plan to get polyu to a high gloss. This is my basic plan.

Hand polish method: Finish with the finest grit sand paper, atm I have 5000grit but heard about up to 12000. Then compound & polish with foam pads. To me hand method is the most important as wood usually is too delicate for any machine work. Since there are sharp edges that wool will cut thru straight away, curved edges etc that a machine will have a high chance of cutting thru.

Machine method: Cut with a rotary buffer w/ double sided wool pad & also swansdown mop. Then use a d/a polisher with cutting & polishing foam pads. More suited for open large areas like a table top. I found the rotary has so much more cut power than a mop on a drill that you really need heaps of experience to use without damaging the clear.

Machine & Hand method: Cut with wool to save alot of time & polish up with hand foam pads. I did this with oil based polyu & it took a while being tough.

Tegmark I look forward to seeing the results.

If you are going to use 2000 grit plus paper make sure you wipe the surface clean between each grade of paper and tack cloth it. It is a real pain if you pick up a loose 1000 grit when using 5000 or higher and it ruining all your work.

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Originally Posted by SPF

Tegmark I look forward to seeing the results.

If you are going to use 2000 grit plus paper make sure you wipe the surface clean between each grade of paper and tack cloth it. It is a real pain if you pick up a loose 1000 grit when using 5000 or higher and it ruining all your work.

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Thanks. I think finishing off with 5000grit looks pretty good, 50/50 matte/gloss.

From all the testing I have done in past few weeks:
- Cheapo brushes are not worth it. My purdy ox hair gives less pinholes than the cheapos. However, thin cheapo does a decent job with very thick coats as you have plenty of film to sand and this brush requires very small acetone to clean.
- There seems to be no reason why a varnish brush gets thrown out after the job, after a dozen or so uses my ox hair seems as good as it was when new.
- Whether coats were very thick, thin, or thinned by 10%. they all bulged up right near edge of wood.
- I found it utterly impossible to work with thin coats as they simply are not thick enough to rub out the pinholes and bulges near edge of wood without causing witness lines and rubbing into stain.
- Unless the surface of wood is perfect like blocked out high build primer and your spraying 3-4 thin coats, the only way i finished a test piece was 5-6 thick coats, thick enough if vertically would result in major runs.
- Visually there doesn't seem to be much diff at all between 3-4 thin coats vs 5-6 very thick. except the latter has a bit more depth perhaps.
- Even if you brush it on like glass without a visual flaw, 30-60mins later pinholes appear probably from the chemical reactions.
- For reasons I don't know, there is always a slight ripply reflection with say a light source while moving against the grain as appose to moving with it. This happens with off the brush, sanded to 5000grit or polished up. whether coats are thick, thin or not brushed. I'm not really sure if this is the grain causing this like an optical effect or just something that plastic poly does? I will try shellac & lacquer one day to see.

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Originally Posted by Tegmark

From all the testing I have done in past few weeks:
- For reasons I don't know, there is always a slight ripply reflection with say a light source while moving against the grain as appose to moving with it. This happens with off the brush, sanded to 5000grit or polished up. whether coats are thick, thin or not brushed. I'm not really sure if this is the grain causing this like an optical effect or just something that plastic poly does? I will try shellac & lacquer one day to see.

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Was this on the same timber (as per previous post in this thread https://www.woodworkforums.com/f9/can...roperly-207490) or something different? How fine did you sand prior and did you use any grain filler?

When I have used it on Teak, Meranti, and another unidentified furniture timber (that I think was poorly cut silky oak), I got the exact same result. It didn't matter how many coats, there was still evidence of grain. In each case it was wet sanded in between coats. I measured it (because I could at the time) and the depth averaged out at about 0.1mm after 3 coats. To be honest, on the pieces of furniture it doesn't bother me because there are no broad flat surfaces. On the meranti window sills it still irritates me when I clean them, but then 15 minutes later it has a layer of salt on it and I can't tell anymore.

On harder timber I haven't found it to be so much of an issue.

BTW thanks for posting up your results above.

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Originally Posted by SPF

Was this on the same timber (as per previous post in this thread https://www.woodworkforums.com/f9/can...roperly-207490) or something different? How fine did you sand prior and did you use any grain filler?

When I have used it on Teak, Meranti, and another unidentified furniture timber (that I think was poorly cut silky oak), I got the exact same result. It didn't matter how many coats, there was still evidence of grain. In each case it was wet sanded in between coats. I measured it (because I could at the time) and the depth averaged out at about 0.1mm after 3 coats. To be honest, on the pieces of furniture it doesn't bother me because there are no broad flat surfaces. On the meranti window sills it still irritates me when I clean them, but then 15 minutes later it has a layer of salt on it and I can't tell anymore.

On harder timber I haven't found it to be so much of an issue.

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Hi SPF.

It was on all of my test pieces that are pine & tas oak. How obvious this is depends on how flat & glossy the top clear surface is. I sanded the raw wood with 180grit & some 240 & did not use any grain filler as at the time I was lazy as these were just small pieces & to me the grain of tas oak was too small & I thought to just fill them up with the clear. Maybe its the lack of grain filler that does this? I fill try this my self as I have never used grain filler.

On another old piece of generic hardware ply that has 6 thick coats of oil based polyu on it, it is extreme by comparison to these test pieces. It really looks like the surface is rippled at certain angles.

Thanks for your help.

Here is a long opening about 2mm deep that is see thru filled with poly.

https://s13.postimg.org/kiuahgrdf/woo_crack_clear.jpg

At first I filled the crack up fully with a small fine brush, but afterwards much of the clear rises up out onto the surface, so it took me about 5 fills.
Then I sanded surrounding surface area with 80-120. Then finished off whole piece with 180 so opening is filled with clear flush to surface.
Then I added thin coat of clear just on the surface of crack with very fine brush. When staining whole piece the stain didn't take to the clear over opening & then I cleaned it up with alcohol on a fine pointy rag.
Later added 1st clear coat over whole piece later & built up coats.

Want to try this on some larger open knots but I think it will take ages as when clear is too thick it always has trapped air bubbles. I tried the epoxy on small openings, but it still makes fine air bubbles.



Here is why I only do very thick coats with 2pack.

https://s17.postimg.org/5fthed5u3/wood.jpg


Its just impossible for me to sand out pinholes without rubbing through on the edges, at very least the final coat would have to be very thick & the bulges/rises will show under the final coat.