On Thu, 13 Mar 2008 08:41:49 +0000, John wrote:
***Is it more concentrated at the base than top. Therefore
concentration of citric acid should be less at top?
I look at it more of damage vs. effect. The softer or more porous (or
just more affected) need less concentration. Otherwise, I'd go as high
as possible for maximum effect. Too high and you can see the damage with
a microscope, even a magnifying glass. I looking for maximum bleaching
with minimum fiber damage. Porosity vs. location, I'd expect more
differences with heartwood vs. sapwood than top to bottom, although at
the extremes new growth vs. old growth could definitely be different.
***Have you tried using a microwave to kill the fungi?
No, only for drying and killing bugs/worms. Sounds reasonable.
I'll give it a try for some of my spalted maple.
Research implies many fungi, including blue fungi, can be killed by
150degf.
http://www.fpl.fs.fed.us/documnts/techline/ii-2.pdf
I have a large drying oven I use for seashells and often use this instead
because you can control humidity while raising heat. Used to prep boards
for bending and to kill bugs in thick pieces or to control drying evenly.
Microwave sometimes splits blanks because of hot spots and it's difficult
to reach and hold a specific temperature. i.e. kill the bugs without
drying.
Another idea I've played with is UV for bleaching, not cleaning.
Apply a frisket or stencil and use strong UV to bleach a pattern before
applying finish -think sandblasting with light. It works great with dark
woods. Used in combination with burnishing to achieve a palette on one
board, great for 3D optical and depth illusions. I've wondered what
affect shortwave UV (dangerous) or high intensity longwave UV might be
able to achieve. As with most processes, too much often causes damage
instead of working better.
Hot sand burnishing
http://www.taunton.com/finewoodworki...AndTechniques/
SkillsAndTechniquesArticle.aspx?id=29464
Another idea I want to try sometime is fuming.
http://www.woodweb.com/knowledge_bas...white_oak.html
Just for fun, this machine could do incredible CNC burnishing, check out
the toast:
http://www.evilmadscientist.com/article.php/candyfab