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Semi-transparent sections in top
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=22123		 Page 1 of 1
Author:  George Thomas [ Sat Apr 25, 2009 10:09 am ]
Post subject:  Semi-transparent sections in top
I recently purchased some Port Orford Cedar tops. After running them through the planer to get a better look at the wood each top set had two areas of darker wood each about 1 1/2" wide. These were parallel to the grain and ran the whole length of the top. I did not think too much about this as I sometimes use old growth WRC that is streaky but really stiff. After making up one set into a top, putting in the rosette then thinning and profiling the top I noticed when I held the top up to light the dark areas were now almost transparent when compared to the rest of the top. Clearly this is more pitch in the wood. My question is how does this affect the strength of the top? Anyone with experience with this? I guess the real question is whether to use the top or dump it. Thanks.
Author:  Bruce Dickey [ Mon Apr 27, 2009 2:25 pm ]
Post subject:  Re: Semi-transparent sections in top
photos ? George?

with and without light would be a big help.

never used Port Orford
Author:  George Thomas [ Mon Apr 27, 2009 2:34 pm ]
Post subject:  Re: Semi-transparent sections in top
Hi Bruce:

I have photos and will post them as soon as I figure out how to do that.
thanks.
Author:  George Thomas [ Mon Apr 27, 2009 2:58 pm ]
Post subject:  Re: Semi-transparent sections in top
Here are front lit and back lit pics. This has not happened on other Port Orford Cedar I have used.
Author:  Mike Collins [ Tue Apr 28, 2009 1:42 pm ]
Post subject:  Re: Semi-transparent sections in top
George;
What is the tops thickness?

The coloration can be mineral deposits or; large late growth due to a very wet growing climate.
If it's stable and aged (dry) I'd use it.
But check with your client (if selling the guitar) for approval of the looks.

Mike [:Y:]
Author:  George Thomas [ Tue Apr 28, 2009 3:13 pm ]
Post subject:  Re: Semi-transparent sections in top
Mike:
The top is thinned to .080" to .082" at this point. If I finish the guitar it will be a little less around the edges - maybe .075".

I plan on setting this top aside to see if there are changes over time. The rest of the sequential batch of Port Orford tops I bought are going back to the supplier. His thought is that the wood is not dry. Possible, but the wood was supposedly air dried for 2 1/2 years after resawing and it has been in my RH controlled shop for five months. I am wondering if the heat from the drum sander had anything to due with the darkening of the streaks. The unthinned tops also had the same semi-transparent look. I do not have a moisture meter but will take the top to someone who does.

"Client" - good one. I wish they were lined up at the door. This guitar is the third prototype for a small bodied, nylon string guitar (12 7/8" across the lower bout). It also has steel-string sized neck of 1 3/4" or 1 11/16" at the nut. And will have a bevel arm rest and other subtle features to make playing easier. There is a commission pending but she is waiting to test this prototype and the changes I have incorporated at her request. The potential client is a long time professional musician so has good reasons for the suggestions she makes.
Author:  Mike Collins [ Tue Apr 28, 2009 5:46 pm ]
Post subject:  Re: Semi-transparent sections in top
George;
do you have tops to replace this one?
The sander could heat resins in the top-but i doubt that's the problem.
It's aged enough for that NOT to be the problem.

Sending them back is the best idea !!
You made the right choice !
P.O. Cedar is expensive & great cuts are rare .
At least on this side if the country !!!!

Is there any reason you can not use another wood for the top ?

Just thinking out loud -trying to help you as much as I can !

Mike [:Y:]
Author:  Mark A Thorpe [ Tue Apr 28, 2009 6:03 pm ]
Post subject:  Re: Semi-transparent sections in top
First off I have never used P. O. Cedar and I know nothing about it. But isn't .080 to .082 thin for a cedar top? This is just a question, something to put in my book of knowledge.
Author:  Alexandru Marian [ Tue Apr 28, 2009 6:41 pm ]
Post subject:  Re: Semi-transparent sections in top
PO cedar is not similar to western red cedar. It is a cypress actually and can be as dense and tough as a very dense spruce.
I did not use it myself yet, but did a lot of research and reading on the subject as I am fascinated by this specie and will definitely try it in the future.
Author:  Mark A Thorpe [ Tue Apr 28, 2009 6:46 pm ]
Post subject:  Re: Semi-transparent sections in top
Wow, thanks for the reply. I would have guessed that it was soft like other cedars.
Author:  George Thomas [ Tue Apr 28, 2009 11:25 pm ]
Post subject:  Re: Semi-transparent sections in top
Mike:

I have other tops except for the four sent back. The wood is dry - I checked with friend's moisture meter. And, tapping the top, it sounds different in the darker areas. Still a mystery, but I can salvage the rosette. Thanks much for the input.

Mark:
As Alexandru said, Port Orford Cedar is not soft like Western Red Cedar. In a good piece of 3A or 4A it will be almost as white as Engelmann Spruce but stiffer and denser, thus can be thinner. In another guitar of the same model (it is small) with a AAAA Western Red Cedar top I thinned the top to .070" or around 1.8mm at the edges. The Port Orford could go thinner on a guitar this small. This model guitar is also a nylon string guitar with a relatively short scale.
Author:  Bruce Dickey [ Wed Apr 29, 2009 8:31 am ]
Post subject:  Re: Semi-transparent sections in top
Looking at the backlit photo it appears you are seeing pitch or resinous streaks. This is very much the same look of a pitch pocket on spruce.

I had some Adirondack with the occasional pitch pocket, and it has this amber translucense.

Looks like you made up your mind not to use it. Everyone I've heard mention Port Orford Cedar is it's wonderful smell.

I agree that for the size instrument this is, .110 to .125 seems more in line, but only if it mirrored the properties of spruce and western red cedar.
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