Re: Wood panel preparation (Keith?)
The letter designation is not that much important to me since the wood will be covered with considerable amnt. of ground - knots and such will not show. What is actually important is the resin and glue they use to bring the veneers together. The stock I ordered uses E1 grade phenol-formaldehyde resin/glue, and this one keeps its properties even at 100C boiling water. Yes I also was considering to seal the edges with polyurethane or epoxy. Thanks for mentioning. I didn't opt for MDF right because of weight. The stock I ordered is 675kg/m3, which means each 13x17" panel will weight about 2 pounds. How that compares to MDF? Regards, Loris. 25 Şubat 2009, Çarşamba, 12:40 am tarihinde, Keith Gerling yazmış: > 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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