|

Production update on the Thuyền thúng Coracle

I have been experimenting with materials and my seemingly rigorous tests have really put the kibosh on a strict papier mache regime. The glues act  to transmit   the moisture and the adhesion collapses. Weighed down on the bottom of a tank, the sunken craft turns to lumpy porridge.

The standard solution of using an outer coating of 2 pack polyurethane is not what I want to do.  But I was researching waterproof coatings for outdoor wood and concrete  and considered 'acrylic elastomeric coatings'  -- which while they will suit the job as an outer coating, may be too heavy for papier mache.( so I am told by the paint company).

But really, my consultant said, a very good acrylic/latex outdoor  paint  will do the  same job at much less cost.In fact boaties here swear by a house paint acrylic -- Dulux Weathershield for their boat exteriors above the waterline.Any below the waterline paint is  usually an expensive enamel . But today the preference has run to using 2 pack polyurethane. rather than enamels.

Another key consideration was that i wanted to recoat the craft maybe annually if necessary and enamel -- and polyurethane especially -- doesn't lend itself to that easily. With acrylic you wash, sand back a bit and paint. All with water clean up too.

So now I'm experimenting with   Weathershield -- all weather -- acrylic house paintto which I've added an acrylic paint condition Floetrol .

The additive gives we a longer dry time and easier, smoother  spread. But the trick I'm exploring is a bit lateral -- I'm using the acrylic paint as an adhesive so that I'm making the model (for now only models) out of Kraft paper and acrylic house paint layer by layer.
Full House/Coracle
I wear disposable gloves and find that I have to dunk the Kraft paper tears in the paint then scrunch them up and wring the paper so that I get a deeper embed of the acrylic. I then apply it by hand to the shape and smooth it down by massaging the layers together.

The acrylic mix however makes the shape very flexible, and I wanted much more stiffness. With a standard papier mache mix I'd get a stuff result.
Is it the paper or the paint? What if I experimented with newsprint? Should I consider adding cotton or linen (or canvas?) ragging?
The blend of paper and acrylic can be torn  along a seam (like cotton can be) if I don't manage a good level of thickness. So  I have to think this is a multi layer project and I may need reinforcement by embedding  other materials beside paper.( eg: bamboo, cotton, linen etc?) So far I haven't worked out how to best mesh the paper layers for greater strength and stiffness.

The general lesson is this: if this works then you could make any structure out of paper and  outdoor  acrylic paint so long as you re-coated at intervals while it was outside. But the internal structure would remain dry. as each layer is protected by its own coating of waterproof paint utilized as a glue.

How strong and waterproof is this paper acrylic mix? I'm still doing tests. But obviously as an option to using standard papier mache glues, it works. Paint technology -- esp house paint technology -- is a big deal esp over the last 10 years and the ability of the paint to adhere to surfaces, even suspect surfaces, is seriously addressed in the lab and in situ.

I laid down maybe ten layers of Kraft paper and now have a convex frisbee  that flexes (more than I wanted). So I'll sand back the top layers and lay down some more paper  to see what impact more coatings have on stiffness.I'll also need to explore other materials in the mix such as canvas, linen ( which I will next)& cotton. (I'm thinking that I'd crisscross strips of these materials to see  if (a) they adhere and (b) they strengthen and (c) give the shape rigidity.

0 comments:

Post a Comment