Aussie products for building a plywood sink

hoffy · Jan 23, 2014

Greetings all,

On the request of my wife, I need to re-adjust the temporary bench space that I use in our laundry (that has become pseudo permanent at the moment). What my plan is now, is to build a light weight semi-permanent bench. As things go, I am now contemplating making this into a smallish darkroom sink.

I was going to make it out of PVC sheeting, but have decided that using standard Ply will be simpler (I can just screw and glue and the shape is done). The biggest hurdle is getting plywood (my local hardware stores only generally sell thin sheets) and my knowledge of making ply waterproof!

OK, what common Australian products (hence why I posted in the Australian sub-forum) should I be looking for to waterproof ply, to a standard that will hold water for 8 or so hours? Or should I actually coat it in fibre glass sheeting and epoxy? Or are there other materials I should be considering?

Cheers

Dave Swinnard · Jan 24, 2014

Ok, so I'm not in Australia (but I was for a few weeks last spring...), but I just made a new darkroom sink.

Rather than use something exotic, like yourself I went with a plywood type material, based upon my current skill set and available tools.

After reviewing the options I settle for a plywood product that's call MDO (medium density overlay) up here. It's basically a plywood, made with waterproof glues with a surface covering of a paper product that is saturated with resins. It's sold as a base material for outdoor signs amongst other uses. See: Dead Link Removed for a bit more info.

The question remains as to whether you can source something similar in your neighbourhood. (maybe check with local sign painters)

The resin soaked paper is very smooth exhibiting none of the pattern/texture that telegraphs through applied coatings.

I built the "box" of the sink using waterproof glue using the 12mm thick product. I tacked the joints with my brad nailer rather than screws as there is less jostling of the joint. Once I had the box built I put thickened epoxy fillets on all the inside corners and then several coats of unthickened epoxy for final waterproofing. Based on my less than skillful epoxy, I feel I obtained a perfectly usable sink. It's not the prettiest as my first batch of epoxy was with an old batch of hardener so it's darker than the other coats, but it's a darkroom sink, not art. (NOTE: the undersides of the sink have a series of wood cross members as reinforcement for the bottom when it's got water in it. PM me if you want more details/photos)

Hope this information is of some use.

JamesR · Jan 24, 2014

Have a look at marine ply.

hoffy · Jan 24, 2014

JamesR said:
Have a look at marine ply.

Thats what I thought as well, but from the research that I did today, marine ply was more about its construction, as opposed to its out and out waterproofing capabilities. From what I have read, you still need to seal marine ply. I thought, that if this was the case, I might as well just use normal ply and make sure its well coated.

Dr Croubie · Jan 24, 2014

Yeah, I was also going to say marine ply, even bunnings sells that (I saw it when looking for a piece of wood to turn my bath into a table for enlarger).
It works well enough outdoors (my dad built me a cubby house when I was a few years old, 20 years later it was still standing). But I wouldn't call it waterproof, unless you absolutely soak it in some kind of epoxy stuff. If you know how to fibreglass, I'd go that route.

Why not try one of those salvage joints, like the one on South road somewhere near Richmond road, for a cheap old steel sink? Just the weight factor?

hoffy · Jan 24, 2014

Dr Croubie said:
Yeah, I was also going to say marine ply, even bunnings sells that (I saw it when looking for a piece of wood to turn my bath into a table for enlarger).
It works well enough outdoors (my dad built me a cubby house when I was a few years old, 20 years later it was still standing). But I wouldn't call it waterproof, unless you absolutely soak it in some kind of epoxy stuff. If you know how to fibreglass, I'd go that route.

Why not try one of those salvage joints, like the one on South road somewhere near Richmond road, for a cheap old steel sink? Just the weight factor?

I suppose I am looking at a fullsize sink where I can just put trays in, ect. I am not really just after a small tub, if that makes sense.

The other thing is it can't be TOO big either!

AgX · Jan 24, 2014

Over here there are at least three Qualities:

-) standard laminated

-) laminated with wateresistant glue-layers

-) planes sealed with waterproof (black-brown) layers (though all edges will still be unsealed)

A interesting alternative might be Wood-Plastic-Composites. But the only easily available forms are small terrace boards, not large, homogenous panels. Furthermore these are intended to be usede as they are. Varnishing them would be difficult due to the used resin. And they seem to be offered typically in wood colours.

hoffy · Jan 24, 2014

OK peeps,

I think this should be rough and ready enough:

Size - It will need to be no longer then 1000mm and probably around 780mm wide - this will fit at 3 16 x12 trays.....just
Sides no higher then 200mm
I'd say I would use probably 9mm or 12mm standard grade ply. I want to be able to screw it all together
All the joins would be sealed with silicon
A plastic waste
once constructed, cover the inside of the sink with fibreglass resin, without the fibre sheeting
frame out of timber and on wheels/castors - I want to be able to wheel the thing around if needed
and make sure the wife approves of the changes before I build it.....

I'll also use the temporary bench that I already have. This will be more then suitable for additional trays if and when needed

Does this sound viable enough?

bdial · Jan 24, 2014

Do you have any shops that do spray-on truck bed liner? For example, this stuff; http://www.linex.com

If you need it to be light weight, build it with the 9mm material, then add additional strips of 9mm to strengthen the stress areas, especially the bottom, or use 12 for the bottom, and 9 elsewhere.

SMBooth · Jan 25, 2014

I just used 16mm structure ply from Bunnings. Glue and screw together and paint with 2 part marine paint, which you will find costs more than the rest of the sink.

pbromaghin · Jan 25, 2014

Jesus, Hoffy. Good luck making your wife happy.

Ian David · Jan 25, 2014

Before babies turned up, and after much research, my plan was a sink built out of 16mm exterior ply, then coated with West Systems epoxy (resin 105 + hardener 207). The sink is built, but it is still not coated yet. I read good things about the West epoxy elsewhere on APUG.
Ian

Kevin Caulfield · Jan 25, 2014

Ian David said:
Before babies turned up, and after much research, my plan was a sink built out of 16mm exterior ply, then coated with West Systems epoxy (resin 105 + hardener 207). The sink is built, but it is still not coated yet. I read good things about the West epoxy elsewhere on APUG.
Ian

So, when do you expect to finish, how long ago did the babies turn up, and did you work out where they are coming from?

Ian David · Jan 25, 2014

Babies started turning up a couple of years ago, and the last one arrived about 6 months ago. I have a fair idea where they are coming from, Kevin
I am hoping to get the sink coated and up and running this year, but that job is currently classified as 'elective'...

hoffy · Jan 25, 2014

Thanks guys.

I got a semi grunt and nod of half approval from SWMBO, so I will step tentatively into the project. I think having it on castors is the main factor that may mean I will get away with it! I have realised that its going to be tight getting it through the door if I need to remove it - something I just need to keep in mind (I already have a cunning plan, just means a redesign of the trolley).

As for the finish, I have found a stockist of the West system close to me - it seems to be only marginally more expensive the Fibreglass resin, so I think I will use that.

Off to the hardware store in the morning!

Cheers

cluttered · Jan 28, 2014

hoffy said:
Off to the hardware store in the morning!Cheers

Once you've finished yours, you can start building one for us

Barry Kirsten · Jan 28, 2014

I built a large darkroom sink out of common materials and used it for many years until I sold it. I needed something deep, and big enough to take four 16x20 trays. Basically I used 8"x1" pine for the sides and ends, screwed and glued together and with a metal "L" bracked across each corner. The base was simple masonite, supported on several cross-pieces and an underneath bede around the perimeter. I let a drain outlet into one end (where I glued an extra pad of masonite underneath for extra thickness). The secret of the whole thing was that ordinary materials could be used, because all of the wet surfaces were coated in several coats of polyester resin - the type that's used for setting fibreglass mat. I had no trouble with the sink in the 15 or so years I had it. This sort of thing is very do-able. Good Luck.

Barry

polyglot · Jan 29, 2014

Definitely make it fit through a door.

I would suggest that 12mm ply is the absolute minimum thickness and sufficient only if you have a big structure of ribs underneath. Once filled with water, the sink may need to support 100kg+ and you want to make sure the structure is good enough for that without the bottom falling out or the legs folding up under it. Most of the sink designs I've seen are 19mm marine ply.

On marine ply, there are two aspects: the glue used and (more importantly) the lack of internal voids. Non-marine ply can have plies overlapping at joins, which leads to little voids, in which water can sit and fester. Yes you still need to seal it, but it lasts better than normal ply in a damp environment.

You can buy the epoxy used for fibreglassing, mix it up and slap it on with no glass mat, and there you have a waterproof coat. I believe there are less-nasty (and cheaper) versions based on polyester that are maybe easier to work with.

I had big plans for a sink but ditched them: I just use a classic small stainless sink in one end of the darkroom/laundry bench, with the Jobo sitting just next to it. No trays 'cos the Jobo will process prints to 16x20". Much prettier than an epoxied plywood monstrosity and (I would assert) much higher WAF even if my Jobo is always parked in the laundry. But then, I do 90% of the laundry work anyway so she doesn't need to care that it's also fitted out as a darkroom.

AgX · Jan 29, 2014

Long time ago I considered making a sink myself from plywood. As 2-compound epoxy varnishes were not commonly available then, I even did not think of them. Instead I planned to use 1-component PVC varnish. That should yield a chemically very resistant but still a bit flexible coating. The fumes of those special solvents are nasty though.

hoffy · Jan 29, 2014

Hmmm, I have to admit I am re-thinking my strategy. I visited the local Bunnings on the weekend to get some sizes and such of certain materials, but didn't get any further.

Like I said, I have a laundry tub for drainage and washing. The main reason behind the sink was as a tempering bath and to control splashes. I have been using trays on benches for ages and I think I have only had to temper outside of my Jobo once. This is going to possibly become a bit of a luxury and maybe not really required.

I think I might go back making a simple bench top. This will also give me additional flexibility, so larger trays don't necessarily need to 'fit'.

polyglot · Jan 29, 2014

Have you seen my built-in benchtop? I recommend talking to a company like Duraprod (these guys are local to me which means not so much for you) that will custom-cut you a nice 38mm laminated benchtop in the finish pattern of your choice, to the exact size you need. You plunk that down on top of cupboards (Bunnings flatpack in my case), bolt the whole lot to the wall and run a bead of silicon around the edge. Looks very professional even if I do say so myself.

I think I spent about $1000 on completely refitting the laundry/darkroom, which got me: 3 of 600x800x600* floorstanding cupboards, 2 of 800x800x300* wallmount cupboards and a 2450x650 benchtop. Washing machine is under the bench between a pair of the cupboards. It took a weekend to install it all (and the weekend before that to cut slots in the brick wall to run new plumbing and wiring), though I've been a lazy bastard and not done the tiling.

When I sell/rent the place, it will be an excellent laundry and I added way more to the house value than I spent on it.

* WxHxD.

Nige · Jan 29, 2014

I got my sink made out of plastic sheet (not sure of type, it's white and about 5mm thick and just glued together but I don't ever fill it with water so no idea if it would actually hold water although it has a deep well section where the drain is and that holds water without leaking fine). It sits on std kitchen joinery cabinents. It's 12years old and looks pretty much the same as the day I installed it. I have 200mm sides but I'd get lower ones if I did it again as I like to rest my butt on a stool while agitating prints and that means I have to reach over the sink edge a little. When standing it works fine. No idea of cost but not having to paint with some fancy 2 pack finish would even it up a bit I'd think.

Aussie products for building a plywood sink

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