Advice on doing a 2Pac Finish

[BobL]

BTW have a look at this
https://www.woodworkforums.com/f67/cy...90#post1768182

[Tegmark]

Probably

If you let it fully cure it's like a rock and sanding becomes much harder - hence the belt sander to get the dents out of the surface.



Complete removal is only for previous coats other than 7008.
The only trouble i had it attaching to an old coat was a couple of spots that were not clean.
When I recoated I did attack the old coat pretty savagely with a belt sander but that was just to get the dents out otherwise in not dented areas I just sanded it until it was smooth


Sorry can't help you there.

Thanks BobL

[SPF]

Probably

If you let it fully cure it's like a rock and sanding becomes much harder - hence the belt sander to get the dents out of the surface.



Complete removal is only for previous coats other than 7008.
The only trouble i had it attaching to an old coat was a couple of spots that were not clean.
When I recoated I did attack the old coat pretty savagely with a belt sander but that was just to get the dents out otherwise in not dented areas I just sanded it until it was smooth


Sorry can't help you there.

+1

Be careful of the temperature and humidity when using 7008. I have used this product extensively for furniture, architraves, and other bits and pieces. I am careful with the mix ratio (digital scales) and I have found that despite the claimed pot lift of 8 hours, it varies considerably. The hotter and drier it is, the faster it tends to gel. Also, take note of the manufacturer's warning about Part B degrading once opened. My experience has been that the older the Part B is (after opening) the faster it gels once mixed. I've had 7008 gel and become unusable within 2 hours in hot dry whether when the Part B can was opened a week or two prior.

I always wet sand between coats with a small amount of biodegradable detergent in the water, and then wipe down with a damp cloth.

In case you haven't found it, the specification sheet can be found here: http://lpb-dev.azurewebsites.net/Upl...pol%207008.pdf

I hope that helps.

[Tegmark]

+1

Be careful of the temperature and humidity when using 7008. I have used this product extensively for furniture, architraves, and other bits and pieces. I am careful with the mix ratio (digital scales) and I have found that despite the claimed pot lift of 8 hours, it varies considerably. The hotter and drier it is, the faster it tends to gel. Also, take note of the manufacturer's warning about Part B degrading once opened. My experience has been that the older the Part B is (after opening) the faster it gels once mixed. I've had 7008 gel and become unusable within 2 hours in hot dry whether when the Part B can was opened a week or two prior.

I always wet sand between coats with a small amount of biodegradable detergent in the water, and then wipe down with a damp cloth.

In case you haven't found it, the specification sheet can be found here: http://lpb-dev.azurewebsites.net/Upl...pol%207008.pdf

I hope that helps.

Thanks. Man those times going gel sound pretty bad. Good to know though. In summer I usually store stuff that was opened under the house where its cold & dry.

[Tegmark]

For those who use 7008, do you bake your project after a coat to speed up the curing time? Can this be done safely like 2pack in the automotive industry? Besides saving time, it would allow to use the left over already mixed parts A & B which are said to only have a pot life of 8hrs.

Do you even bother with re-coat times? Or just feel if it's not sticky to the touch you can just sand & add another coat?

[SPF]

For those who use 7008, do you bake your project after a coat to speed up the curing time? Can this be done safely like 2pack in the automotive industry? Besides saving time, it would allow to use the left over already mixed parts A & B which are said to only have a pot life of 8hrs.

Do you even bother with re-coat times? Or just feel if it's not sticky to the touch you can just sand & add another coat?

I have never baked 7008 and never would. The thing to be careful of when baking timber (apart from isocyonate, flamability hazards, and ensuring that the temperature of the work piece is below 35 degrees when you put on the next coat) is relative humidity and moisture content in the timber.

If you heat it up too much the moisture near the surface under the paint can cause delamination and make the finish look milky/cloudy.

If you have a ventilated powder coating oven or paint booth that you can try it out in, I'd be interested to see your results - but I suggest doing it on a couple of scrap pieces before painting a family heirloom or anything else of value. Like most 2 pack paints you have to use adequate safety measures - the MSDS can be searched for here: Product Finder : Valspar Professional

[Tegmark]

I have never baked 7008 and never would. The thing to be careful of when baking timber (apart from isocyonate, flamability hazards, and ensuring that the temperature of the work piece is below 35 degrees when you put on the next coat) is relative humidity and moisture content in the timber.

If you heat it up too much the moisture near the surface under the paint can cause delamination and make the finish look milky/cloudy.

If you have a ventilated powder coating oven or paint booth that you can try it out in, I'd be interested to see your results - but I suggest doing it on a couple of scrap pieces before painting a family heirloom or anything else of value. Like most 2 pack paints you have to use adequate safety measures - the MSDS can be searched for here: Product Finder : Valspar Professional

Thanks SPF, I didn't think about the moisture in wood. But what if the whole wood is 'sealed' by clear & its around 45C temp? Seems like an easy to achieve temp without being too high.



I have some other Q's about 7008, I assume you should sand it wet or dry with gloves to protect from the isocyanates unless it's fully cured?

If the mixed parts are stored in a sealed jar can they still be used a day or two later at room temp? My mixed parts haven't gone hard in the sealed jar yet.


Finally, would 7008 be great for outdoor UV, heat & cold exposure? If not what other easy applied products in 2pack are there? For the record oil based canned PolyU is terrible outdoors. In 2years outside on side of house it flaked off wood looking soo bad.

[SPF]

I have always sanded back to timber before applying the 7008, so I don't know about baking sealed timber. Like I said, if you go ahead and try it I'd be interested to know your results.

I sand it with a little water with some biodegradable detergent in it, and then wipe it clean with a damp cloth. At times the 7008 can be a little tacky even when it is fully cured. Tacky is probably overstating it, more like it is grippy on the sand paper. The detergent cleans the surface and makes sanding a lot easier.

I think I'm misreading your question about mixed parts. My mixed 7008 (Part A and Part B) always gels within the stated 8 hour pot life, so no you can't use it days later. If your mixed paint is not gelling within this time there is something wrong.

If you have a look at the spec sheet it states that it is an indoor paint only. I (and my family) have used 7008 on window frames inside, but that are exposed to direct sunlight for hours a day. All of these have lasted for more than 10 years. Some have started to become less clear but the paint is still intact, and a couple have cracked where the timber is subject to significant thermal cycling.

My preference for clear finishes outside are either a quality latex acrylic (easy) or using epoxy resin as a base coat and then finishing it in a marine 2pac polyurethane (difficult, costly, and risk to health). In cases where I do the latter, I also use a light fibreglass cloth with the epoxy to protect the timber from gashes and scratches that allow moisture into the timber - its a lot of work, but if you do it properly, you don't have to do it again for a decade or two.

I hope that helps.

[ian]

3- With Pot Life, what does 8hrs standard & 1hr fast mean in terms of mixing ratios?

while not specific to 7008, with SystemThree epoxy adhesives / finishes, the hardener is rated as fast, normal, or slow. The idea is that at low temperature you use the fast hardener to pull the curing time back to something reasonable (like 6 to 8 hours), while at higher temps you use the slow hardener to push the pot life out to something reasonable (like 30 to 40 minutes).
In terms of mixing ratios, the different hardeners are formulated in a way to keep the mixing ratio constant regardless of which hardener you are using.

[BobL]

Thanks SPF, I didn't think about the moisture in wood. But what if the whole wood is 'sealed' by clear & its around 45C temp? Seems like an easy to achieve temp without being too high.

A hot shed in summer would reach that temp, you could always try that. On a quality piece of furniture I would be worried by the wood expansion and shrinkage between 45 and 20ºC as epoxy is generally not as flexible as PU.

The first time I recoated our kitchen bench it was the middle of summer and because of the sanding and fumes involved I turned off the air-conditioner and opened up the windows and i remember over the 3 days it took it was stinking hot and the inside temperature reached >28º. The next time was the end of May and as we run no heating appliances in our house and let it cool right down it was much cooler probably around 17º. I don't recall any significant differences in curing time between the two coatings.

To sand the bench the first time I used a Makita belt sander with the crappy little dust bag and the just filled the house up with dust.
The second time I attached a shop vac with a dust exit port and attached some 2" hose to that and dangled that out a window and this made a big difference.
I then did the same with the ROS between subsequent coats although I did mostly wet sanding.

I have some other Q's about 7008, I assume you should sand it wet or dry with gloves to protect from the isocyanates unless it's fully cured?

I don't know where I read it but I seem to recall reading that when you can't smell it this means the solvent is basically gone and the cyano is locked into the material
I know what feels like to be poisoned by 7008 by handling it when its wet and have also sanded it wet or dry with bare hands immediately after the prescribed sanding time and have felt no effects.
Cyano poisoning is interesting because if you are only exposed to very low levels (which is the case with 7008 absorption through the skin) you can feel the preliminary effects (tingling finger tips and lips) well before you reach a toxic dose.

If the mixed parts are stored in a sealed jar can they still be used a day or two later at room temp? My mixed parts haven't gone hard in the sealed jar yet.

Just because they haven't gone hard doesn't mean it will flow properly when applies.

Finally, would 7008 be great for outdoor UV, heat & cold exposure? If not what other easy applied products in 2pack are there? For the record oil based canned PolyU is terrible outdoors. In 2years outside on side of house it flaked off wood looking soo bad.

7008 like EVERYTHING else is hopeless outside on timber. Remember timber is not like metal and moves even when sealed. Eventually cracks develop and water gets in and you know the rest.

[Tegmark]

I have always sanded back to timber before applying the 7008, so I don't know about baking sealed timber. Like I said, if you go ahead and try it I'd be interested to know your results.

I sand it with a little water with some biodegradable detergent in it, and then wipe it clean with a damp cloth. At times the 7008 can be a little tacky even when it is fully cured. Tacky is probably overstating it, more like it is grippy on the sand paper. The detergent cleans the surface and makes sanding a lot easier.

I think I'm misreading your question about mixed parts. My mixed 7008 (Part A and Part B) always gels within the stated 8 hour pot life, so no you can't use it days later. If your mixed paint is not gelling within this time there is something wrong.

If you have a look at the spec sheet it states that it is an indoor paint only. I (and my family) have used 7008 on window frames inside, but that are exposed to direct sunlight for hours a day. All of these have lasted for more than 10 years. Some have started to become less clear but the paint is still intact, and a couple have cracked where the timber is subject to significant thermal cycling.

My preference for clear finishes outside are either a quality latex acrylic (easy) or using epoxy resin as a base coat and then finishing it in a marine 2pac polyurethane (difficult, costly, and risk to health). In cases where I do the latter, I also use a light fibreglass cloth with the epoxy to protect the timber from gashes and scratches that allow moisture into the timber - its a lot of work, but if you do it properly, you don't have to do it again for a decade or two.

I hope that helps.

Hi, I have stored many pieces in oil based in my shed in summer taking a beating the whole time sealed all around asap after buying the wood. Most of the surface looks fine, apart from some small cracks near wood joins. Wouldn't do it again now.

7008 not fully cured seems the same to sand as oil based. Thanks for your advice

[Tegmark]

7008 like EVERYTHING else is hopeless outside on timber. Remember timber is not like metal and moves even when sealed. Eventually cracks develop and water gets in and you know the rest.

Thanks I think its the wild swings of cold & hot & not the constant UV that kill the clear.

[Tegmark]

Some more Q's I have.

When should I cut & polish 7008 to a high gloss? Or any 2pac PolyU. Before it's fully cured or after? I'm worried if I wait until fully cured it might be soo hard & the required polishing could cause problems. Even oil based PolyU fully cured takes along time to polish up, the results are inconsistent.

When cleaning Brushes with 2pac PolyU, I noticed going through thinners like water & it evaporates too quickly before the detergent can wash it all away, I thought at the end to just use turps & hopefully it would be strong enough to clean the left overs. Turps is cheap, stays wet & washes away well with detergent. Not sure if this is a good idea with 2pac & expensive brushes?

[q9]

Turps is useless with 7008. Acetone. My work system with 7008 cleaning is 3 jars of reducer, and lots of rags/newspaper to clean the brush. Finally soak in acetone. But still, be prepared to chuck brushes more frequently than you'd like. Part of the deal.

[Tegmark]

Turps is useless with 7008. Acetone. My work system with 7008 cleaning is 3 jars of reducer, and lots of rags/newspaper to clean the brush. Finally soak in acetone. But still, be prepared to chuck brushes more frequently than you'd like. Part of the deal.

If the thinners has had a chance to dissolve & flush most of the 2pac, I should think turps will bridge the gap between thinners & detergent well. I will have to try.

From experience cleaning thick varnish brushes with oil based, You have to be relentless cleaning the brush far more then 3 times. & flick violently to get the left overs in the Bristols out.