Finish for Quartersawn Sycamore

[John Coloccia]

Okay, I've been thinking about this for a bit. If you match the coating IOR to the wood, you essentially reduce the reflection occurring at the surface of the wood. I think that has the effect of enhancing contrast because only the most favorable reflections will make it to your eye. That would also increase the chatoyance because the reflections are sensitive to angle. So basically the funny bits that aren't flat (i.e. the figure) get darker. Is that about right?

[Jim Becker]

The one piece of QS Sycamore I've used (a cabinet top in our master bath) was finished "naturally", with BLO, de-waxed shellac and a water borne top coat which is effectively clear.

[sheldon pettit]

hm.... let's try this, the I.ndex O.f R.efraction [IOR], in the sense of it's causing our visual perception to perceive waves or curls etc. in wood in a more dimensional way than when viewing it when it's in a dry state when the only refraction that is taking place is that of normal air, is due to the wetting out of the surface[s], with differing liquids of molecular weight, [density].

That is, to a degree, what the photo is showing, in the sense of the "denser" the clear liquid [in this case] is, the more the light-waves are slowed down as they travel through it. Since the light waves have lost some of their normal [in air] speed and energy, the light is bent at increasing angles as the increase of denser materials are used which progressively slow the light waves down incrementally.


With optics, the same thing happens in the sense or regards to the light being bent due to the density of the solid material, but in it's case it is a tri stimulus result, meaning it first is bent from what it's normal path would be if travelling through air alone and when then it travels through the glass it is bent [slowed down] and then re-emerges and continues it's normal in-air path of direction. [simply put]


If you place a piece of glass on a figured wood surface, it will not, for the above reason, really not change or enhance or improve the DOI[ distinction of image] of the naturally occurring figure of the wood because of it not being able to come in intimate contact with the wood and wetting it out, what you have is an unattached surface that still is causing an air to clear solid and back to air phenomena. In other words the straight line of light curves and then resumes it's normal direction of travel when re-entering the small amount of air in between the glass and the wood. Where as if you were able to melt the glass and attach it directly to the wood, [without destroying it's natural characteristics in doing so, aka - burning or blackening] The optical affect would be permanent and with no air interface create a much improved DOI.


Which for all practical purposes, really just means a better visual ability to perceive the figure affects in a more dimensional way than when dry. The lesser the refraction, the less we visually respond to it dimensionally, the more refraction the more depth and perception increases the dimensionality of what is already present in the dry state and gives us what we perceive as an increase in 3D affects of the surfaces.


If this still isn't clear, then at some point i will write an article after i have gathered enough photos which are much more help visually when explaining such ok?. As they say, a pic is worth a thousand words

[Prashun Patel]

I can't argue with your science, Sheldon. But I can say from my limited experience, I believe that BLO or any amber finish including shellac is better at highlighting the figure because it causes a more drastic color difference between the curl and the noncurly parts.

As for irridescence or the ability for the piece to appear 3-dimensional, I find the biggest bang for the buck is buffing or rubbing out the piece at the end. This suggests that it has something to do with a having a level surface...?

[glenn bradley]

The one piece of QS Sycamore I've used (a cabinet top in our master bath) was finished "naturally", with BLO, de-waxed shellac and a water borne top coat which is effectively clear.

I give Jim a big thumbs up.

[sheldon pettit]

I can't argue with your science, Sheldon. But I can say from my limited experience, I believe that BLO or any amber finish including shellac is better at highlighting the figure because it causes a more drastic color difference between the curl and the noncurly parts.

As for irridescence or the ability for the piece to appear 3-dimensional, I find the biggest bang for the buck is buffing or rubbing out the piece at the end. This suggests that it has something to do with a having a level surface...?

LOL, thanks Prashun, though iridescence has nothing to do with what were talking of here, though I take it as just a remark being made as trying to be descriptive in your language, we can discuss that issue at another time

Amberness can definitely make the wood more "attractive" in the sense of adding color to the film of finish and is what has made oils and finishes of such nature popular for centuries, Or as far as that goes, amberish colored dyes also. So there is no disagreement from me in that sense lol. But no matter what oil you use being ww clear mineral oil or the darkest amber oils, if the "density" of the oils are the same, the DOI will also be for all practical purposes the same also.

The difference you will see is if you use an unthinned BLO orTung for example, as compared to ones that have been thinned out to a good degree, and the comparison is made on applying to wood while still in liquid wet form and viewing is in slight differences as to this depth or perception since the oil molecules still maintain the original density to the same degree thinned or not. Meaning thinning does not destroy their molecular structure but just moves them further apart for a time. For this reason, if you were to drastically reduce the oil of preference say by 95% thinner to 5% oil, it would retain for a while, till dry, more of the RI of the diluent than the RI of the oil. The other way around of course, would have little affect on visual affect you were seeing.

As far as drastic differences in color, as noted, even very thin amber dyes or any color that is soaked into the differing porosity of the the fluctuating grain patterns of figured woods, is more of a "highlighting", as you say, of the interlocking grain areas that go darker as compared to the smoother face grain of the other areas. Just as in painting landscapes or other, darkness in certain areas makes the lighter portions stand out more by creating the appearance of depth between the the two.

Again, as to depth or dimension, the clarity as well as the thickness definitely play vital rolls. As to smoothness, not as much, in the sense of i or others can bring let's say an old antique with wavy surfaces of underlying figured woods to a wet look state of appearance by friction polishing with shellac or other even higher refractive coatings, and have just as much dimensional visual affect as if perfectly flat and smooth. Though there are some resins like many of the acrylic polyester's that because of their resin properties can actually magnify, thus creating even more depth, when ground perfectly smooth or used for encapsulation by use of glass smooth molds, most definitely improve these features quite noticeably. But here again, it is also still due to densities of the substances as well.

[Chris Padilla]

I think we should call Sheldon, Dr. P.

[Prashun Patel]

I suppose I'm out of my league here, so I'll defer to what you've written. Can you tell me what kind of test I can do to convince my eyes of this?

[sheldon pettit]

I suppose I'm out of my league here, so I'll defer to what you've written. Can you tell me what kind of test I can do to convince my eyes of this?

Considering anyone to be either in or out of my or any league is of no concern to me Prashun, i never even give thought to such. It is never my intention to write in such away as to even make anyone feel that they are less equipped than me or someone else in something specific or otherwise. If anyone is ill equipped here it would be me, not you as to trying to explain physics, which by far was not my best subject, as to comparing my knowledge to one who has no or less background in such. If anyone here is ignorant here, it is me, not you or others lol. My dealings with IOR or RI or N/d or any other terms used in explanation of such has been mostly limited to that which is in the field of coatings where these indices are already established without the need to perform them individually to access the results. In other words if a client had need of a high RI in a coating or related material for said purposes as we now talk of i would simply find out what values were being looked for and use materials in that range to give the required end product. Thus, as for testing i have no formal test to show what you ask of me now.

That said, where i would start on my own would be with two closely matched oils to do so, in your case for what your looking for i would choose one that was a water clear oil and compare it to the colored or amber oil for reference. Keeping in mind to dis-include any internal play of color the chromophores present in the LO would contribute to. Again being fare as to observable results, i would also apply an amber dye to the figured maple so that this was even less of a factor. The dye then giving both samples a beginning dark and light contrast in that respect.

To do this again you would mote in the wood with plumbers putty or other material and pour the oils in and observe any visual differences seen as to how they affect the overall look or appearance of the wood as to defining the darkness or lightness factors and the overall depth and clarity as well as any gained dimensionality. in other words, do the darker and lighter areas of one look extremely close or is their a large readily noticeable difference? One you can just glimpse at and easily determine is such is the case. For if it's not readily and easily seen then it's pretty much a moot point as to whether the amberness of one oil against the non amber oil is really justifiable as to it's use as one over the other. Of course none of this will really give proof to the matter unless the density of the liquids match up closely also. In other-words, if one oil is 3 times denser than the other, then results will have no conclusive evidences to go by or base anything upon.

For example, an old trick often performed was one of the disappearing glass, where in for this example Pyrex glass was used, When a mineral oil of heavy density was pored over a partially submerged Pyrex glass the submerged part of the glass became invisible, here again due to the refractive density of the oil. Since the mineral oil comes in three main grades of of density - light medium and heavy, to accomplish the disappearing of the submerged portion of the glass r even when totally submerging it, it is necessary to adjust the density of the oil, by adding about 1/3 of light density to the heavy density, when viewing you can readily see that when the glass is no longer visible, then the amount is correct.

What of curse this causes in the LO and other Clear oil used is a matter of not having a lighter oil of the same type for either to adjust for such. though you could possibly find lighter versions of either oil on the open market, i would not know of such off hand. So if your test turns out to be a wash, at least you'll know why, lol.

[sheldon pettit]

LOL, please don't thanks, i'm far from up to snuff in many areas, remember I'm 65, and new products and additives etc are coming out faster then i can or care to keep up with lol. When were talking of the pre-waterborne era is when I'm at my best and not at my best in physics, lol.