Re: Wood panel preparation (Keith?)
I admit I'm a little confused about what is and what is not "marine grade plywood". Do you know if your plywood has a letter designation? I'm trying MDO, which here: http://www.glen-l.com/wood-plywood/marine-plywood.html could be considered marine grade. It is smooth on both sides and the outside veneer us very smooth, grainless, and artificial - like pressed wood (MDF) but smoother. Marine grade or not, the edges do swell up in the water, so I size to keep the soaks as short as possible. If I omit the size, the soaks can take longer than an hour. I prefer the finish of MDF, which I can buy for $18 for a sheet of 4x8 feet at 1/2 inch. The surface is perfect for gum, and the edges can be sealed cheaply with 2 part marine epoxy. But the stuff is heavy! Very heavy to ship. Prints on the MDF are much more "gumlike" and the ones on MDO are too slick and C-print looking. Oh - and of the pictures that I shared earlier, none of them are on MDO. Later this week I'll have some completed, but I doubt if the difference will be discernable on-line. On Tue, Feb 24, 2009 at 3:50 PM, Loris Medici <mail@loris.medici.name> wrote: > Hi Keith, > > Yes, I'm a little bit meticulous because I have little time devoted to > printing, therefore I don't have the luxury of trial and error, without > risking motivation loss that is... ;) > > That sizing seems pretty weak. (My usual for paper is 3%) Will calculate > by measuring the weight of half tablespoon gelatin -> that should be > pretty close since we have the same stuff. What if I don't size? (I'm > pretty sure you have tried this.) Will that work also? > > I was afraid of long soaks therefore I ordered marine grade plywood (which > is very resistant to water - no warping, no veneer coming apart...), it's > not expensive (considering the material) -> I ordered 25 13x17" sheets, it > will cost me only USD 48, including cutting the huge raw sheet to size. > (Makes less than USD 2 per sheet, and that's cheaper than fine quality > watercolor paper!) > > At your printing size smoothing actually takes something (tactility?) from > the prints but I prefer to work on smaller scale which makes a smoother > surface a necessity. > > See the aluminum sheet I just finished to gesso here: > http://tinyurl.com/dl5wnu > > It was shot under oblique incandescent light, exaggerating the texture. > (The field of view is something like 4x6" - just to give you an idea of > the magnification. 4 layers of acrylic gesso with calcium carbonate, > applied with a foam brush.) Ground formulation as following: 40g gesso + > 80g CaCO3 + 80ml water. > > I like the texture, will sand half only of the sheet and see how each side > behave... The surface is very nice, feels very absorbent and soft to the > touch -> very similar to an eggshell. (That's fine I presume...) > > Scotch pad idea is great -> will try that first. Yes, I'm concerned about > the dust -> I don't think Elif will appreciate it! :) > > Thanks again, > Loris. > > > 24 Şubat 2009, Salı, 5:40 pm tarihinde, Keith Gerling yazmış: >> Well, here is where we may go our separate ways, because we are >> meticululous and me?... not so much! >> >> Sizing Strength: I don't actually know. I use a half tablespoon of >> Jelatin (Toz - no idea of the bloom) to 450 ml water to which I add >> about 3 ml Gluteraldahyde. >> >> Coating: I'm using two surfaces at present. MDO is a very smooth >> plywood used for signs and for boatbuilding, but I'm not sure if it is >> actually "marine grade". MDF is a heavy pressed wood. MDO is very >> smooth so it takes three coats of the affore-mentioned gesso. MDF >> requires only two. I'm sure a roller would be great. I prefer a big >> rough brush, as I like the brushstrokes. I do not sand, as this >> provides a surface that is too smooth and perfect. Something tells me >> this is the method you will prefer :) - When I did sand I just used a >> rough screen - the type used for smoothing drywall plaster, or a 3m >> scotchpad green thing - sandpaper made a big mess - the pumice powder >> got into everything. >> >> >> >> 2009/2/24 Loris Medici <mail@loris.medici.name>: >>> Thanks Keith! As I understand it, I need to increase the whiting amnt. >>> in >>> my preliminary formula, since I choose to mix equal *weight* of acrylic >>> gesso with whiting (50g gesso + 50g CaCO3), but you say equal >>> *volumes*... >>> That was good to know. Thanks for the info about sizing. >>> >>> Few more questions: >>> - What is your sizing solution strenght? >>> - What is your coating method? (Detailed description please; how much >>> layers? exact application method and procedure? - crossing fingers: I >>> want >>> to be able to coat with a foam roller...) >>> - Do you sand the acrylic gesso before sizing? If yes, how? What is your >>> exact procedure? >>> >>> I feel like leaving the "traditional gesso" plan behind, it's too much >>> complicated for my liking -> I may resort to it if everhing else fails, >>> but I'm afraid it has its own problems as it looks like a method that >>> should be mastered - painfully! >>> >>> Thanks again & regards, >>> Loris. >>> >>> >>> 24 Şubat 2009, Salı, 4:22 pm tarihinde, Keith Gerling yazmış: >>>> Hi Loris! >>>> >>>> The #1 formula you present is very similar to the one I use with great >>>> success: 1:1 Liquitex acrylic gesso to water and then to that 1:1 >>>> dilute gesso to pumice by volume. That produces a surface that acts >>>> very similar to paper, so I size it with gelatin and hardener. This >>>> mix is very good for coating porous surfaces such as wood, plaster >>>> (spackle-ed wood) and old gumprints on paper. For surfaces such as >>>> aluminum and glass, bubbles of water tend to form between the surface >>>> and the gesso with long soaks. For these surfaces I do not use >>>> acylic, preferring to mix up a concoction of gelatin, pumice and >>>> marble powder. I haven't used this in a while and I haven't reduced >>>> it to a recipe, but essentially it is a gelatin mix (the same as used >>>> for sizing paper) with 50% pumice and marble. It produces a surface >>>> that is so hard that it is actually very hard to remove even with a >>>> belt sander! >>>> >>>> Hope this helps >>>> >>>> >>>> >>>> On Tue, Feb 24, 2009 at 2:30 AM, Loris Medici <mail@loris.medici.name> >>>> wrote: >>>>> I will try to print gum on wood panels (marine grade plywood). I will >>>>> try >>>>> two different grounds: 1) Acrylic ground + whiting (I presume that's >>>>> what >>>>> you do Keith?) 2) Traditional gesso ground... >>>>> >>>>> 1) Keith, what is your acrylic formula? I plan to dilute acrylic gesso >>>>> 1:1 >>>>> with water and then add equal amnt. of calcium carbonate (marble dust) >>>>> and >>>>> some white pigment into it. For instance: 50g acrylic gesso + 50ml >>>>> water >>>>> + >>>>> 50g calcium carbonate + 10g titanium dioxide (titanium white -> purest >>>>> / >>>>> brightest white pigment). >>>>> >>>>> 2) Traditional gesso: 100ml water + 10g hide (or rabbitskin) glue >>>>> (high >>>>> bloom gelatin) + 60g calcium carbonate + 12g titanium white. >>>>> >>>>> I need a good working recipe and application (and finishing) procedure >>>>> for >>>>> #2. BTW, traditional gesso is a PIA! (Have to keep it hot + it doesn't >>>>> set >>>>> quickly, so takes awfully long to complete 4 - 6 layers...) >>>>> >>>>> Another questions: >>>>> >>>>> 1. Do you harden the traditional gesso ground? >>>>> >>>>> 2. Do you add a hardened gelatin layer on top of the acrylic (or >>>>> traditional gesso) ground? >>>>> >>>>> Thanks in advance, >>>>> Loris. > >
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