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Asphalt colorant
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Dave Chandler
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Joined: 31 Oct 2007
Posts: 669
Location: Mt Mitchell in North Carolina

PostPosted: Mon May 18, 2015 8:23 am    Post subject: Asphalt colorant Reply with quote

I've used asphalt as a colorant and have now filtered my varnish 3 or 4 times through coffee filters, and still getting little specks I presume from the asphalt. Will this settle in time or is it just a cost of using this material? Maybe a better way to filter this varnish?

Its a beautiful color, with some Alazarin Crimson added to bring out some additional red. I'm hoping if I just let it settle a couple weeks, maybe it will be usable.
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Dave in the Blue Ridge
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L P Reedy
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Joined: 02 Apr 2009
Posts: 241
Location: Brevard, NC

PostPosted: Mon May 18, 2015 3:50 pm    Post subject: Reply with quote

What is your asphalt source? I use high purity roofing asphalt but dissolve it before adding and have never filtered varnish. I suspect the specks may be something other than asphalt but can't tell from here.

Lyle
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Dave Chandler
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Joined: 31 Oct 2007
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Location: Mt Mitchell in North Carolina

PostPosted: Mon May 18, 2015 5:19 pm    Post subject: Reply with quote

Its roofing asphalt, disolved in turpentine, and is like a thick gum. It has been filtered several times before adding it to my varnish. I mix a dollop in 50/50 varnish/turpentine. Heat it up, and strain it a few times. I lose a little with each pass, but can't seem to get it all out.

I may just give it a week or so and see if it settles.
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Dave in the Blue Ridge
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DonLeister
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Joined: 29 Mar 2007
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Location: Richmond, VA

PostPosted: Mon May 18, 2015 9:02 pm    Post subject: Reply with quote

A paper coffee filter? Seems like that would get the particles out.
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Dave Chandler
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Joined: 31 Oct 2007
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Location: Mt Mitchell in North Carolina

PostPosted: Tue May 19, 2015 7:36 am    Post subject: Reply with quote

I'm going to try again, disolve a glob of my tar in about 20x as much turp, filter it as many times as I can without losing it all, then boil the excess turpentine off to get it back to a density I can add it back into my varnish. Maybe that'll do the trick. Is it possible I'm getting something from the paper filters?
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Dave in the Blue Ridge
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DonLeister
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PostPosted: Tue May 19, 2015 8:12 am    Post subject: Reply with quote

You probably know this but turps will leave or turn into a resin of sorts over time so your mix will be slightly different . I like Gamsol or mineral spirits which dissolves the tar I have really well.

I have had some thinners degrade the container liners and become contaminated to the point where filtering was necessary.


Last edited by DonLeister on Tue May 19, 2015 8:34 pm; edited 2 times in total
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Dave Chandler
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Location: Mt Mitchell in North Carolina

PostPosted: Tue May 19, 2015 9:34 am    Post subject: Reply with quote

I'm finding that my raw varnish is contaminated, although I don't underrstand why it hasn't filtered out. I'm puzzled.
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Dave in the Blue Ridge
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DonLeister
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PostPosted: Tue May 19, 2015 8:45 pm    Post subject: Reply with quote

What is your raw varnish btw?

I have this idea in my head, and it may be just speculation but it seemed like when I used turpentine as a thinner that it attracted more dust and when I use mineral spirits things have less dust.
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Dave Chandler
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Joined: 31 Oct 2007
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Location: Mt Mitchell in North Carolina

PostPosted: Tue May 19, 2015 11:54 pm    Post subject: Reply with quote

Its simply resin cooked down with linseed oil (3/2 ratio) and a bit of lavender oil, then added in some turpentine to keep it fluid to get it into bottles. Its about the consistency of honey when cold, I add turp about 1/3 to get it fluid enough for application with brush, and dries to the touch in about 3 hours in bright sunlight, or about 24 hours in my light box. Not sure what got in, this is the first batch I've made, so I wasn't sure what to expect. I'm checking, I poured into several bottles, maybe its just one bottle. Not sure how I'm going to filter this all out, probably dilute, reheat, filter, then cook off excess turp. You think mineral spirits might be better? My wife would like that, she hates the smell of turpentine.
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Dave in the Blue Ridge
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Michael Darnton
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PostPosted: Wed May 20, 2015 8:28 pm    Post subject: Reply with quote

If oil varnish is overcooked, it develops little bits that supposedly can't be filtered out (I've never done this, so I don't know by experience.) Oil varnish should only be cooked until a finger pressed to and drawn from a cooled drop forms a line line a spider web and not a bit longer.
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Dave Chandler
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Joined: 31 Oct 2007
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Location: Mt Mitchell in North Carolina

PostPosted: Wed May 20, 2015 10:45 pm    Post subject: Reply with quote

Thanks Michael, that's what I was watching for. I used that same technique, put a drop in water, then put it between thumb and forefinger and could get a thread to develope when you pull them apart. I kept looking to get a longer thread, and when it was apparent that the thread was starting to get shorter, took it off the heat. I could have gone a bit too long.

I supposed it could be re-crystalizing after I spread it, and this might explain what is going on. Perhaps I need to try a few other thinners other than turpentine, see if that changes this phenomena. I can think of a few I might try.
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Dave in the Blue Ridge
Southern Violin Association

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DonLeister
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Location: Richmond, VA

PostPosted: Wed May 20, 2015 11:00 pm    Post subject: Reply with quote

Your varnish sounds like a reasonable recipe.

Odorless mineral spirits definitely helps. Turps will never just evaporate, it does something and changes chemically into a resin. That's how Fulton type varnishes are made, you take turps and bubble air through it for a month or three and it gets thicker and more amber colored, resembling sap from the tree, but it's not, it's something different.
I made a batch of Fulton varnish which is useful, but is a rather tough varnish which won't wear hardly and polishes something like plastic.

Oh yea, most turps these days is really stinky because it comes from about anywhere in the world and who knows what industry it is a by-product of. There is one place in the US that makes it from the traditional tree in a traditional manner and is worth getting, that would be Diamond G products in Georgia.
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Dave Chandler
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Joined: 31 Oct 2007
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Location: Mt Mitchell in North Carolina

PostPosted: Wed Jun 03, 2015 7:11 pm    Post subject: Reply with quote

Now its recrystalising in the jar, so maybe I didn't cook it long enough or hot enough (using a hot plate on max -- maybe should put it on the barbeque).
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Dave in the Blue Ridge
Southern Violin Association

"Success is the ability to go from one failure to the next with no loss of enthusiasm" Winston Churchill

"I took the road less travelled, and now I don't know where I am." Marco Polo
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Mat Roop
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Joined: 24 Mar 2007
Posts: 813
Location: Wyoming Ontario

PostPosted: Thu Jun 04, 2015 8:59 am    Post subject: Reply with quote

Dave I know nothing about varnishes, and next to nothing about roofing asphalt.
Modern asphalts often have additives creating what is known as rubberized asphalt that lays down better and is less brittle. Often, other stuff is also added as fillers.
So getting asphalt from a roofer should be ok.. but be sure it is pure bitumen.
Fwiw... Mat
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byacey
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Joined: 29 Mar 2008
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Location: Edmonton, Alberta

PostPosted: Wed Jul 01, 2015 12:53 pm    Post subject: Reply with quote

A roofer gave me a brick of this stuff. If you hit it with a hammer, it breaks open like glass, and even looks like black glass where it's fractured. I don't think there's any rubbery characteristics about this particular product.
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