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ctviolin
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Joined: 07 May 2009
Posts: 961
Location: Roswell
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 Posted: Sat Oct 05, 2013 9:10 pm Post subject: Problem - Question |
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Recently I posted here about how I plane the edges of split billet halves before I join them, with a 22" joining plane and a shooting board, in order to get the plate edges absolutely flat first.
Which as always, for many years has worked perfectly well, the back plate (Maple) joined with no visible glue line along its length - which is the desired result, and, the more difficult of the two plates to get right.
The top plate, (Sitka Spruce) which was much easier to plane flat, also joined with no gap as expected, but the glue line showed up as a sort of stain that made a thin discolored mark along where the join is.
I checked the quality of the plate for flatness of the cut before joining (as always), and when I look along the join line now - even with my lupe - it is as close (in other words - touching and no gap) as it ever is...
I've never had this type of discoloration along a join line before.
The glue was freshly made pure hide glue and used immediately.
Any ideas why? Should I post a picture?
I believe it will be no problem to varnish this completely away, I'm just not sure what or why this happened...???
(I did check the join for strength, in case it was faulty that way, but it is as strong as possible - or as is usual with fresh hide)
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Michael Darnton
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Location: Chicago
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| Posted: Sat Oct 05, 2013 11:31 pm Post subject: |
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Iron contamination is a common cause. In my building, I have to use bottled water for my glue because of the 100 year old pipes. Also if you use acid brushes or brushes with any metal on them for gluing, rust can get in the glue and stain, also. The glue doesn't have to look bad when you do it--iron discoloration develops over a short period of time.
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ctviolin
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Joined: 07 May 2009
Posts: 961
Location: Roswell
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| Posted: Sun Oct 06, 2013 9:25 am Post subject: |
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| Michael Darnton wrote: | | Iron contamination is a common cause. In my building, I have to use bottled water for my glue because of the 100 year old pipes. Also if you use acid brushes or brushes with any metal on them for gluing, rust can get in the glue and stain, also. The glue doesn't have to look bad when you do it--iron discoloration develops over a short period of time. |
Wow, thanks for the heads up.
I never thought about impure water, but here in Roswell we have continual problems with old piping... work crews (and homeowners) are always working, digging up different sections of the street, and their yards and homes, to replace it.
And - it tastes bad.
Bottled water it is then.
And thanks again for a simple solution to this problem.
You da man! (OK, sorry, I couldn't help myself...)
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actonern
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Joined: 15 Aug 2007
Posts: 444
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| Posted: Sun Oct 06, 2013 12:47 pm Post subject: |
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In your case I'd blame the obvious culprit...
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Janito
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Joined: 08 Oct 2007
Posts: 114
Location: USA
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| Posted: Sun Oct 06, 2013 4:16 pm Post subject: |
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A few years ago i jointed 13 tops and backs.
When all was done, 1 top had the 'dark line'. When I inspected closely there was no glue line, but more a tinting of the wood adjacent to the join. Weird.
This was old spruce probably >30 yrs old that I brought from the the UK - did not happen in joints of Engelmann and another sort of spruce. |
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ctviolin
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| Posted: Sun Oct 06, 2013 4:18 pm Post subject: |
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| actonern wrote: | In your case I'd blame the obvious culprit...
AREA 51
Ha Ha Ha |
Hey!!
I'm not allowed to talk about that...
ct
(rhymes with ET - did you notice?)
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ctviolin
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| Posted: Sun Oct 06, 2013 5:35 pm Post subject: |
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| Janito wrote: | A few years ago i jointed 13 tops and backs.
When all was done, 1 top had the 'dark line'. When I inspected closely there was no glue line, but more a tinting of the wood adjacent to the join. Weird.
This was old spruce probably >30 yrs old that I brought from the the UK - did not happen in joints of Engelmann and another sort of spruce. |
very interesting...
I did not see any line on the back wood that I joined, but now that I know why it's there on the front, I have decided that it simply wasn't visible because the maple is colored more that the spruce...
But the truth is, that when I inspect the back very closely, even though it's darker wood, and more difficult to see - there simply is no "rust" line there - it simply didn't form on the back plate.
Only on the top plate.
And it is a "rust" sort of stain in the spruce, so it must only "show" when the conditions are right for it to form.
I'm thinking that the cure (pure, clean H20) is worth turning to for all joining now, just to remove the chance of having it happen again, when the conditions are "right" for it to happen. (well perhaps "right" is not the word to use, perhaps I should say when the conditions are "wrong" ...)
Now that I know why it happened, I can avoid it ever happening again. No matter what wood I choose.
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kjb
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| Posted: Sun Oct 06, 2013 7:18 pm Post subject: |
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| i wonder if it is possible that you can cut the grain in such a way that it refracts in a dark way my last one did that but it is hard to notice after the varnishing, maybe just a fluke on my part. |
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John Masters
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Joined: 13 Mar 2013
Posts: 23
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| Posted: Fri Oct 11, 2013 12:33 pm Post subject: Re: Problem - Question |
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| ctviolin wrote: |
I've never had this type of discoloration along a join line before.
The glue was freshly made pure hide glue and used immediately.
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Hi Craig,
I always take an 1/8" slice over the broad face of the halves with a bandsaw. Even if you can't see much darkening of the wood, it will often show up after glued. Even if it is slight, I don't like it. For me, it is the much-valued suntan or oxideation confined to a narrow strip.
For the Sitka I promised to send, this is very important, as it has been sitting around for years. After you cut your slice, you can compare the colors. Also, and handy, you can split the sheet to see the grain orientation in the middle of the planks.
This is important for sitka, I think it darkens more quickly than other kinds of spruce. I believe it has more tannins, but don't know.
John |
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