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 <email@example.com> 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:
> 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,
> 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 <firstname.lastname@example.org>:
>>> Thanks Keith! As I understand it, I need to increase the whiting amnt.
>>> my preliminary formula, since I choose to mix equal *weight* of acrylic
>>> gesso with whiting (50g gesso + 50g CaCO3), but you say equal
>>> 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
>>> 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,
>>> 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 <email@example.com>
>>>>> I will try to print gum on wood panels (marine grade plywood). I will
>>>>> two different grounds: 1) Acrylic ground + whiting (I presume that's
>>>>> you do Keith?) 2) Traditional gesso ground...
>>>>> 1) Keith, what is your acrylic formula? I plan to dilute acrylic gesso
>>>>> with water and then add equal amnt. of calcium carbonate (marble dust)
>>>>> some white pigment into it. For instance: 50g acrylic gesso + 50ml
>>>>> 50g calcium carbonate + 10g titanium dioxide (titanium white -> purest
>>>>> brightest white pigment).
>>>>> 2) Traditional gesso: 100ml water + 10g hide (or rabbitskin) glue
>>>>> bloom gelatin) + 60g calcium carbonate + 12g titanium white.
>>>>> I need a good working recipe and application (and finishing) procedure
>>>>> #2. BTW, traditional gesso is a PIA! (Have to keep it hot + it doesn't
>>>>> 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,