Options please for finishing sycamore bowls/platters
-
We just finished moving the forums to a new hosting server. It looks like everything is functioning correctly but if you find a problem please report it in the Forum Technical Support Forum (click here) or email us at forum_moderator AT aawforum.org. Thanks! -
Beware of Counterfeit Woodturning Tools (click here for details) -
Johnathan Silwones is starting a new AAW chapter, Southern Alleghenies Woodturners, in Johnstown, PA. (click here for details) -
Congratulations to Dave Roberts for "2 Hats" being selected as Turning of the Week for April 22, 2024 (click here for details) -
Welcome new registering member. Your username must be your real First and Last name (for example: John Doe). "Screen names" and "handles" are not allowed and your registration will be deleted if you don't use your real name. Also, do not use all caps nor all lower case.
"best" finish
- Thread starter cwearing
- Start date
Need more info
What is your goal, Gloss, natural feel and warmth... is it going to be used?
What is your goal, Gloss, natural feel and warmth... is it going to be used?
decorative---semi-gloss
Is the sycamore green, dry, spalted, etc?? I've only turned spalted sycamore, and it really soaked up the finish. It took several times as much as any other woods I've used. I can't speak to green wood that isnt spalted...
My suggestion would be
As much sanding sealer as it will soak up, then about a 60 sheen lacquer.
As much sanding sealer as it will soak up, then about a 60 sheen lacquer.
Finishing Sycamore....fume, seal, finish....
First - if you want to heighten the contrast between the darker 'flecks' and paler "background" wood, you can fume the piece with ammonia, I've had good luck doing this to make the distinction between the fleck figure and pale wood more pronounced - it's particularly attractive on quartersawn parts of the piece where the fleck is accentuated. I sand to at least 320 before fuming, and then sand at 400 to remove any 'fuzzies' that may have been raised by the humidity from the ammonia fuming treatment. Be sure the piece is fully dry before final sanding.
I then seal with a one pound cut of ultra blonde shellac, knock that back with steel wool (00, then 0000), and then use spray lacquer (pre-cat / nitrocellulose). to finish.
I find that this shellac/lacquer finishing method alters the colors of the wood the least (i.e. no color shifting with polyurethanes or darkening with oils), yet it preserves and enhances the intricate cellular detail that is so interesting in sycamore.
Rob Wallace
First - if you want to heighten the contrast between the darker 'flecks' and paler "background" wood, you can fume the piece with ammonia, I've had good luck doing this to make the distinction between the fleck figure and pale wood more pronounced - it's particularly attractive on quartersawn parts of the piece where the fleck is accentuated. I sand to at least 320 before fuming, and then sand at 400 to remove any 'fuzzies' that may have been raised by the humidity from the ammonia fuming treatment. Be sure the piece is fully dry before final sanding.
I then seal with a one pound cut of ultra blonde shellac, knock that back with steel wool (00, then 0000), and then use spray lacquer (pre-cat / nitrocellulose). to finish.
I find that this shellac/lacquer finishing method alters the colors of the wood the least (i.e. no color shifting with polyurethanes or darkening with oils), yet it preserves and enhances the intricate cellular detail that is so interesting in sycamore.
Rob Wallace
Last edited:
ammonia
What is the chemistry behind the amonia fuming. Also, please describe the procedure for the fyming process.
What is the chemistry behind the amonia fuming. Also, please describe the procedure for the fyming process.
Fuming with Ammonia
First, I am not a chemist; I only have some very limited knowledge about the chemistry of the ammonia fuming process. My assumption is that there is a differential deposition of tannins or other polyphenolics that are more concentrated in the darker 'fleck' areas, relative to the paler background wood cells. Ammonia (or ammonium ion) interacts with these compounds and produces either some form of complexing, or establishing chromophores that absorb more light (?). [I would be happy to learn more details and obtain a better explanation about the chemistry of this process from organic or natural products chemists.] (My earlier experience with ammonia fuming was in the lab, studying flavonoid mixtures from plants that were separated on 2-dimensional chromatograms, using ammonia fuming and viewing UV light to observe chromatic shifts in fluorescence to identify the separated compounds).
In sycamore, the ammonia fuming will slightly darken the background 'pale' wood, but will selectively darken the fleck features to a greater level of 'darkness', heightening the contrast (there may be some variation between batches of wood as to ability to establish this contrast). It has long been known that fuming cherry, for example, can produce a deeper, richer tone in the wood. I have also found this true for Goncalo Alves, which deepened the color intensity on the darker areas (presumably with more tannins or other extractives), and was only of minimal influence on the lighter (sapwood) areas. There is much room for experimentation here...
As to the fuming process, it is fairly simple. The unfinshed (but sanded) wood piece is placed in a closeable container (or "tent" if very large) - I use a gasketed-lid 5 gallon plastic container (such as a "drywall compound bucket"). A small container of liquid ammonia is placed into the large container with the piece to be fumed, such that it does not touch the wood. I support the turned wooden piece off of the bottom of the large container (a small amount of wire mesh works OK) so that ammonia fumes can reach all sides of the piece at the same time. I use laboratory grade concentrated ammonium hydroxide for this, but household ammonia sold as a cleaning agent will work as well - it just takes longer. A rolled-up piece of paper towel that extends above the rim of ammonia vessel (I use a 250 ml glass beaker) serves as a "wick" which provides more surface area for the ammonia to evaporate from. Partially fill the ammonia container with liquid ammonia solution after the towel is saturated. The large container is then sealed, and the fumes are allowed to concentrate and interact with the wooden piece until the desired effect is reached. This may take one day, one week, or even more time - variables include the species of wood used, temperature, ammonia concentration, and probably some individual variation in the specific piece(s) of wood being used. It's a trial and error - "wait 'til it looks good" - kind of process.
A word of caution - Ammonia vapors are noxious, and in high concentration, dangerous. I would not advise doing this procedure in an indoor shop/studio unless there is a VERY good ventilation system available. When I do ammonia fuming, it is usually done in my garage from spring to fall when temperatures are high enough to do this within a reasonable period of fuming time (I live in Iowa, with cold, often "sub-zero winters"). To check on the fuming progress, the cover is opened carefully outdoors, so as to avoid breathing the fumes; I stand upwind so that I do not encounter the escaping ammonia fumes. (When I've ammonia fumed in winter months, I do it in my lab at the University, and uncover the container within a chemical fume hood - one of the perks of being a science nerd!) As might be obvious (or not?), do not breathe ammonia fumes, use proper eye protection, and avoid getting liquid ammonia on exposed skin.
Once the piece is "done" to the desired level of darkness, it is removed from the fumes and allowed to out-gas and dissipate any residual ammonia vapors. This is usually completed in a day or two, depending on temperature. You can easily tell when this is done by cautiously sniffing the piece.
Because the fuming was done in an enclosed, highly humid container, there may be wood fibers raised during this process (you can easily feel if this has happened). Some light sanding with 320 or 400 can usually remove these "out-standing" fibers without cutting too deeply into the wood surface. From there, I seal with 1# shellac and then spray lacquer as noted in my earlier post.
Hopefully this is clearly explained enough for others to try the process...
Let me know if there are questions....Vaughn - let me know if the fuming process works on your sycamore...
Rob Wallace
First, I am not a chemist; I only have some very limited knowledge about the chemistry of the ammonia fuming process. My assumption is that there is a differential deposition of tannins or other polyphenolics that are more concentrated in the darker 'fleck' areas, relative to the paler background wood cells. Ammonia (or ammonium ion) interacts with these compounds and produces either some form of complexing, or establishing chromophores that absorb more light (?). [I would be happy to learn more details and obtain a better explanation about the chemistry of this process from organic or natural products chemists.] (My earlier experience with ammonia fuming was in the lab, studying flavonoid mixtures from plants that were separated on 2-dimensional chromatograms, using ammonia fuming and viewing UV light to observe chromatic shifts in fluorescence to identify the separated compounds).
In sycamore, the ammonia fuming will slightly darken the background 'pale' wood, but will selectively darken the fleck features to a greater level of 'darkness', heightening the contrast (there may be some variation between batches of wood as to ability to establish this contrast). It has long been known that fuming cherry, for example, can produce a deeper, richer tone in the wood. I have also found this true for Goncalo Alves, which deepened the color intensity on the darker areas (presumably with more tannins or other extractives), and was only of minimal influence on the lighter (sapwood) areas. There is much room for experimentation here...
As to the fuming process, it is fairly simple. The unfinshed (but sanded) wood piece is placed in a closeable container (or "tent" if very large) - I use a gasketed-lid 5 gallon plastic container (such as a "drywall compound bucket"). A small container of liquid ammonia is placed into the large container with the piece to be fumed, such that it does not touch the wood. I support the turned wooden piece off of the bottom of the large container (a small amount of wire mesh works OK) so that ammonia fumes can reach all sides of the piece at the same time. I use laboratory grade concentrated ammonium hydroxide for this, but household ammonia sold as a cleaning agent will work as well - it just takes longer. A rolled-up piece of paper towel that extends above the rim of ammonia vessel (I use a 250 ml glass beaker) serves as a "wick" which provides more surface area for the ammonia to evaporate from. Partially fill the ammonia container with liquid ammonia solution after the towel is saturated. The large container is then sealed, and the fumes are allowed to concentrate and interact with the wooden piece until the desired effect is reached. This may take one day, one week, or even more time - variables include the species of wood used, temperature, ammonia concentration, and probably some individual variation in the specific piece(s) of wood being used. It's a trial and error - "wait 'til it looks good" - kind of process.
A word of caution - Ammonia vapors are noxious, and in high concentration, dangerous. I would not advise doing this procedure in an indoor shop/studio unless there is a VERY good ventilation system available. When I do ammonia fuming, it is usually done in my garage from spring to fall when temperatures are high enough to do this within a reasonable period of fuming time (I live in Iowa, with cold, often "sub-zero winters"). To check on the fuming progress, the cover is opened carefully outdoors, so as to avoid breathing the fumes; I stand upwind so that I do not encounter the escaping ammonia fumes. (When I've ammonia fumed in winter months, I do it in my lab at the University, and uncover the container within a chemical fume hood - one of the perks of being a science nerd!) As might be obvious (or not?), do not breathe ammonia fumes, use proper eye protection, and avoid getting liquid ammonia on exposed skin.
Once the piece is "done" to the desired level of darkness, it is removed from the fumes and allowed to out-gas and dissipate any residual ammonia vapors. This is usually completed in a day or two, depending on temperature. You can easily tell when this is done by cautiously sniffing the piece.
Because the fuming was done in an enclosed, highly humid container, there may be wood fibers raised during this process (you can easily feel if this has happened). Some light sanding with 320 or 400 can usually remove these "out-standing" fibers without cutting too deeply into the wood surface. From there, I seal with 1# shellac and then spray lacquer as noted in my earlier post.
Hopefully this is clearly explained enough for others to try the process...
Let me know if there are questions....Vaughn - let me know if the fuming process works on your sycamore...
Rob Wallace