Actually, you're right that it's a science. When Chris and I were working back at Kodak (starting to sound like "this one time at Chemistry camp"), we studied solvent evaporation for coatings. This is essentially what we were dealing with. Polyurethane is only soluble in so many things. But what determines how well it sets is actually dependent on solubility, boiling point, vapor pressure and saturation point. Amongst other things that I can't remember off the top of my head. Yeah, acetone boils off quicker and will probably allow it to dry quicker but how would the coating look afterwards. In the adhesives industry, a fast boiling solvent would be used only to "blister" the adhesive so that it aerates it. Useful in adhesives in bandages so that your skin can breathe. But adding the wrong solvent in, you can make it white (trapped air) or make it so that it takes forever to cure. Although Chris and I are somewhat familiar with the science of it, making wood shiny still ultimately requires a LOT of skill and technique. That's where sites like this come in handy. Thank you Al Gore for inventing the internet :icon_scra
polyurethane techniques
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J
jeff...
Travis Naptha is a great goo getter, like cleaning up scotch tape residue, grease, oil and lables goo, it also doubles as lighter fluid for wick based lighters, if your on the cheap :lol:.
Xylol on the other hand is a strong solvent but gives me a bad headache and makes me feel wierd, I loose my fine motor skills and makes me a bit dizzy, so I stay away from it if I can.
J
jeff...
:rotflm:
When it comes to removing goo or adhesive residue, I usually reach for a can of brake cleaner. Other than the CO2 propellant, it's 100% tetrachloroethylene. It removes duct tape residue like nobody's business and evaporates cleanly.
Somebody mentioned that polyurethane is dissolved. Is this correct or is it a suspension?
Somebody mentioned that polyurethane is dissolved. Is this correct or is it a suspension?
Been doing it for years.
If some of you guys don't have Bob Flexnor's book, I strongly suggest that you get a copy.
>> So, we have Arm/R... and Waterlox. What kind of material is used in that? How durable is it and what are the drawbacks? "
Let me clear up a couple of points. Arm-R-Seal is a thinned wiping varnish. The varnish components are alkyd resin and linseed oil (in spite of the incorrect info given out by David Marks). The Waterlox Original Sealer/Finish is an oil heavy phenolic resin and tung oil varnish. It can be used as a wiping or brushing finish without thinning. It's higher oil content means it is softer and more flexible than the Arm-R-Seal and somewhat less durable. The Phenolic resin makes it a dark amber color. It works well in high moisture situations and on darker woods. It tends to be too yellow on light light colored woods.
If you want to use a wiping varnish you have a number of choices. One is to use a product already thinned like the Arm-R-Seal, Watco wiping varnish or Waterlox. You can also easily make your own by thinning a standard varnish or poly varnish 50/50 with mineral spirits. I much prefer to use a non-poly varnish as it gives a clearer finish but poly varnish certainly an alternative if you want slightly higher abrasion resistance.
Whether you use a pre-mixed wiping varnish or mix your own, a satin finish will require that the material be well stirred as I said in my other posting. With a heavily thinned finish, the flatteners tend to drop out of suspension very quickly. Stir you material every couple of minutes or you may end up with sort of gray areas or gray streaks in the finish.
If you end up using the wiping technique, let me know and I will post some instructions that may be helpful.
Let me clear up a couple of points. Arm-R-Seal is a thinned wiping varnish. The varnish components are alkyd resin and linseed oil (in spite of the incorrect info given out by David Marks). The Waterlox Original Sealer/Finish is an oil heavy phenolic resin and tung oil varnish. It can be used as a wiping or brushing finish without thinning. It's higher oil content means it is softer and more flexible than the Arm-R-Seal and somewhat less durable. The Phenolic resin makes it a dark amber color. It works well in high moisture situations and on darker woods. It tends to be too yellow on light light colored woods.
If you want to use a wiping varnish you have a number of choices. One is to use a product already thinned like the Arm-R-Seal, Watco wiping varnish or Waterlox. You can also easily make your own by thinning a standard varnish or poly varnish 50/50 with mineral spirits. I much prefer to use a non-poly varnish as it gives a clearer finish but poly varnish certainly an alternative if you want slightly higher abrasion resistance.
Whether you use a pre-mixed wiping varnish or mix your own, a satin finish will require that the material be well stirred as I said in my other posting. With a heavily thinned finish, the flatteners tend to drop out of suspension very quickly. Stir you material every couple of minutes or you may end up with sort of gray areas or gray streaks in the finish.
If you end up using the wiping technique, let me know and I will post some instructions that may be helpful.
So, lets say I have some adhesive on some polyurethaned furniture due to childproof bumpers that have been removed. Can I use the brake cleaner on that?
J
jeff...
Travis I would use napha on that, tetrachloroethylene is wicked, is a Carcinogen: A substance with the ability to cause cancer.
see this CDC fact sheet on tetrachloroethylene ATSDR - ToxFAQs™: Tetrachloroethylene (PERC)
Thanks
see this CDC fact sheet on tetrachloroethylene ATSDR - ToxFAQs™: Tetrachloroethylene (PERC)
Thanks
OSHA/NIOSH says the permissible exposure limit/time weighted average (sustained amount you can be exposed for for an 8 hour day) is 100 ppm. The threshold for being able to smell it is around 1ppm. Using a quick squirt on a rag to wipe off some adhesive isn't going to cause cancer. Granted, I woudn't want to speend all day every day breathing 100 ppm TCE, but I don't hesitate to use it.
FWIW, here's a link to the NIOSH pocket guide to hazardous chemicals. It's a pretty useful resource if you're wanting to use a solvent in the shop and you want to get a feel for how dangerous it is. It's a little more terse (and if you ask me, more informative) than an MSDS. Warning, it's a 18MB .pdf file. Here's the NIOSH pocket guide to hazardous chemicals homepage.
Travis, when it comes to using it on a finished surface, I'd be really careful. Test it in a spot that's not visible to make sure that it's not going to eat through the polyurethane. I don't have any experience using it on a wood surface. I've used it mostly on plastics and metal/painted metal. Let me know if you try it though, I'd be interested in what you find out.
FWIW, here's a link to the NIOSH pocket guide to hazardous chemicals. It's a pretty useful resource if you're wanting to use a solvent in the shop and you want to get a feel for how dangerous it is. It's a little more terse (and if you ask me, more informative) than an MSDS. Warning, it's a 18MB .pdf file. Here's the NIOSH pocket guide to hazardous chemicals homepage.
Travis, when it comes to using it on a finished surface, I'd be really careful. Test it in a spot that's not visible to make sure that it's not going to eat through the polyurethane. I don't have any experience using it on a wood surface. I've used it mostly on plastics and metal/painted metal. Let me know if you try it though, I'd be interested in what you find out.
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Hostile??? :rolf::rolf:
This was nothing more than a discussion. :lol::lol::lol::lol: Jeff and I both were enjoying the exchange. I think a lot of good info got in this thread because of the discussion.
Trust me, this was far from a thread that would be on of of those "other" forums. :roll::roll:
John
J
jeff...
Chris thanks for the information. From what I've read of your posts, you know much better than I do about chemicals.
Here is something that should help. A friend of mine put it together years ago and it has worked well for many.
QUOTE
There are a number of suggested application regimens that are totally subjective. The number of coats in a given day, the % of cut on various coats, which coat to sand after, when to use the blade and a whole host of other practices are all minor differences between finishers. There are some things that I consider sacred when applying a wipe-on finish.
First, you can use any full strength oil based clear finish. Polyurethane varnish or non-poly varnish is fine.
If you are making your own wipe-on the mix is scientific - thin. I suggest 50/50 with mineral spirits because it is easier to type than any other ratio and easy to remember. Some finish formulators have jumped on the bandwagon and you can now get "wipe on" finish pre-mixed. If you use a pre-mixed, thinning is generally not neccessary. But making your own is cheaper and you know what's in it.
The number of coats in a given day is not important. Important is to apply a wet coat with an applicator and merely get it on. Think of a 16 year old kid working as a busboy at Denny's you have sent over to wipe off a table. Sort of swirl the the material on like you would if you were applying a paste wax. Don't attempt straight strokes. The applicator should be wet but not soaked. The applicator can be a paper towel, half a T-shirt sleeve or that one sock left after a load of washing. Then leave it alone. The surface should not be glossy or wet looking. If you have missed a spot, ignore it - you will get it on the next coat. If you try and fix a missed spot you will leave a mark in the finish.
Timing for a second coat involves the pinkie test. Touch the surface with your pinkie. If nothing comes off you are ready for another coat. If was tacky 5 minutes ago but not now, apply your next coat just as you applied the previous coat. Remember, you are wet wiping not flooding. After applying the second coat, let it fully dry for 48 hours. Using 320 paper and a sanding block ligthtly sand the surface flat. Now, begin applying more coats. Do not sand between coats unless you have allowed more than 24 hours to elapse since the prior coat. The number of coats is not critical - there is no critical or right number to apply. For those who need a rule, four more coats on non-critical surfaces or six more coats on surfaces that will get abraded seems to work.
After your last coat has dried at least over night you will have boogers in the surface. You should not have marks in the surface because you ignored application flaws. You may have dust, lint and, if you live in Texas, bug legs. Use a utility knife blade at this point. Hold it between your thumb and forefinger, near the vertical, and gently scrape the surface. Gentle is the important word - no harder than you would scrape your face. If you start scraping aggressively you will leave small cut marks in the surface. After you have scraped to the baby butt stage gently abrade the surface with 320 dry paper or a gray ScotchBrite. Clean off the surface. Now, leave the area for two hours and change your clothes. Apply your last coat with a bit more care than the previous coats and walk away.
An anal person is going to have a tough time with this process. Missed spots have to be ignored. Wet wipe, don't flood. Scraping to babies butt smooth means scraping no harder than scraping a babies butt. Ignoring any of these will leave marks that are tough to get out. Getting these marks out requires some agressive sanding to flatten out the surface and starting over.
Jim Kull
END QUOTE
Finally, It works better to use a gloss varnish for all coats except the last. The flatteners in semi-gloss and satin tend to rapidly fall out of suspension when the finish is highly thinned. If you want a non-gloss finish, use it only on the final coat or two and be sure to stir the material frequently or you will end up with cloudy streaks.
I was going to say something:angry6wn: . Not because it was that hostile, but because it was said with such absolute certainty (opinionated:lol: ) that a the person asking the question might have taken your comments as absolute gospel.:shocked7fl: Your comments about gloss finish are probably your preferences (and a lot of others). You mentioned not seeing Gloss Finishes in a museum. Let's not forget French Polishing, certainly a well respected "traditional" finish and skill.
Now as far as hostility. You are right that a lot of good information got exchanged because of the discussion, but that would have been achieved by offering your opinions as opinions.
Please remember, everyone, that information provided gently, is usually received more readily than information provided as absolutes.
I will now get off my "high horse" and try to decide how to decide when I want a high gloss finish and when I don't:lol: :eusa_danc
Now as far as hostility. You are right that a lot of good information got exchanged because of the discussion, but that would have been achieved by offering your opinions as opinions.
Please remember, everyone, that information provided gently, is usually received more readily than information provided as absolutes.
I will now get off my "high horse" and try to decide how to decide when I want a high gloss finish and when I don't:lol: :eusa_danc
Thank you Howard, that was extremely helpful
J
jeff...
Mike, you bring up a great point about kids and intended use, one thing that came to mind is a base ball bat. I'm thinking a dead flat polyurathane would be a great finsh for a base ball bat. Heck for that matter adults tear up base ball bats too, now that I think about it.
As for a "hostile thread" I've met John and he's alright, I never once thought our little debate would turn personal. Like I said, it's good to have an adult level conversation and not have to be conserned about it being emotional. And as John said: "I get a kick out of conversations and debates like this. In the end the right answer is up to the end user. What is right for you is right for you.". Anyways, if the conversation would have went south, Steve would have jumped both of us :lol:
Thanks
The one thing I've learned from all this is that there's many ways to skin a cat. (Chris, no Chinese/cat jokes, okay?) It's okay, I didn't take anything as fact but I will take your opinions to heart because it's quite obvious most everybody here knows what they are talking about. I mean, after all, we do get to see some of your work. So please, for my sake, keep those comments coming. I appreciate them. I have even started printing some of them so I can read them off the computer. Thanks again.
You point of "gospel" is right on. It should have been provided in more of a suggestive manner. I do get upset when I whitness folks falling over the same hurdles I did in the learning process. I want to try to save them the agony of a badly finished peice. I've got a couple in my home that aren't shown to anyone but kept as a reminder. One peice was constructed extremely well and I was truely proud of the woodworking and ruined it with the finish. Heck I even went through the experience of Polyshades!!! (Please don't use that stuff :eusa_pray:eusa_pray:eusa_pray)
French polishing (the premier fine finish in most folks minds) is a means of bring a nice gloss up to a table top, instrument and many other fine peices. Rarely though does the entire peice have a super high sheen. Most chippendale, Green & Green, Arts & Crafts, queen anne, or whatever peices have a much duller sheen because a harsh gloss for the entire surface is not desirable.
Steve, this might sound a bit "preachy", but I want to put this out there. Finishing is the dread of most woodworkers, but it shouldn't be. It is your opportunity to make your work really show. You can take an ordinary peice and make it extraordinary with the right finish or you can take an extraordinary peice and make it ordinary with the wrong finish. I urge all new woodworkers to buy a couple good finsishing books and study finishing like they would study jointery. It is just as important. You can practice your finish like you practice cut a dovetail joint. Instead of loathing the finishing process embrace it and learn it. It will become very satisfying. :-o:-o:-o
I'm done now.
John
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