Home made sink
I've seen similar questions in this thread, but none that specifically deals with what I need to ask. so please forgive me if I'm being repetitive..
My darkroom/shed is coming along nicely and I've finally got a nice sink built from MDF. At the moment it's in it's raw state but I want to protect it so that it will last a few years. I have Yacht varnish for a protective coating, and am wondering if Blackboard paint be suitable to paint it with first or is there a specific paint finish that anyone would recommend?
Any advice would be greatly appreciated,
I've learned so much from my mistakes... I'm thinking of making more...
If I recall correctly, MDF can be prone to signifigant swelling when it gets soaked, and swelling can force the rupture of thin brittle paint films, so I think you will want a very good water barrier. I'm not an expert, but I suspect you may find an unadorned paint film fails soon, and that you will be rebuilding before you want.
A lot of people will put a layer of epoxy or of polyester resin on a sink. Either usually reinforced by a layer of fiberglass. Epoxy or polyester resin will saturate the fiberglass and bond to your substrate, MDF.
If epoxy or polyester resin are beyond the scope you wish to undertake, then beefing up the paint film, and reinforcing especially in corners would seem a fair second best. I would stay away from brittle finishes. Flexibility would allow the finish to take impact without failure.
A high grade flexible caulking in all corners would be part of my suggestion.
I just looked at your reference to MDF and it says:
"Drawbacks of MDF: .... Swells and breaks when waterlogged"
That reinforces my inclination to urge you to apply a resilient surface to your sink.
Last edited by CBG; 03-19-2008 at 07:11 PM. Click to view previous post history.
Reason: spelling error
I have used just the two part epoxy resin brushed over plywood. I never needed to use the fiberglass on any of my sinks. The epoxy resin will do the best job for you. I cut in my drain strainer and epoxy right over it to seal it right to the sink. Good luck
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I have an older book here on darkroom/film developing. Can't remember the name right now sorry. The first chapter deals with building a sink. Basicly you make the sink out of wood, lay in a coat of fiberglass resin, QUICKLY lay in fiber matting, another layer of resin, let dry. Drill hole for drain andn install proper hardware. Looks pretty simple and fiberglass is much easier to work with than many people think. Like high tech and stinky paper mache. You just have to work FAST as the resin sets in about 15 minutes.
Síle, I myself am looking into building a new sink for my darkroom. I have thought long and hard and have come up with two solutions, one of which is MDF.
I have MDF bench tops in my factory, we sealed them with a yacht lacquer as you are contemplating, they have been there for 15 years now and apart from wear in some places requiring a re-application of the lacquer, they have been brilliant.
As to painting I have looked into the colour and rejected black as it means you cannot see a dark stain appearing if there is a leak in the lacquer.
I finally found a mid grey coloured waterproof paint which is used on ships, think Navy ships. This appears to be the best product for my new sink.
I also looked at concrete paints but the Naval paint appeared to be the best, although I'm a novice when it comes to actual paint properties.
If some people are thinking that yacht lacquer isn't waterproof then they should look at my motorcycle rack. I'ts made out of normal 3 ply and has been sealed with yacht lacquer. It has been on my motorcycle for the last 7 years and hasn't required any re-sealing, even though it has incurred heavy use with all sorts of luggage being strapped to it and obviously rubbing as it is jolted due to the undulations of the roads and tracks it has traversed.
Síle, I would suggest you seal the MDF on all sides, we had one bench which absorbed moisture from condensate on a wall.
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A more expensive solution, but perhaps a life-long one is to line the sinks with PVC sheeting. I've done it on my two sinks, and I fully expect these sinks to last a very, very long time. The glues used for PVC are quite harsh, so you want to do it outside, if you can. It helps to have two people, since the glue also sets up fast. It cost about $300 Cdn (back when the Cdn/US exchange rate was $1.35) to line two sinks, one 12', the other 8'. Glue was another $50. But, considering that I'll never have to touch these things again, it was worth the expense.
I just finished my sink last week, and used heavy plywood. I used the tried and true polyester resin (the type used for fiberglass) directly onto the sink in 3 seperate coats - wasn't very difficult and makes a very durable and waterproof finish (the sinks at our school darkroom are built this way in the 1970's and see heavy use, and are still perfect). It really wasn't any harder than painting a sink would be - but I did do it outside on a sunny day - it stinks to high heaven and I wouldn't do it inside. Also, use the cheap "chip brushes" for each coat, and throw the brush away when done with that coat - if you use a good paintbrush you will ruin it. If it is good enough for canoes and surfboards, it certainly would waterproof your MDF. I would think the PVC sheeting idea would work well also - I personally wouldn't take chances with varnish or paint, since your substrate is MDF, which falls apart when wet.
Though it is going to be more expensive than MDF, if I were to build my own sink, I would use pressure treated or marine-grade plywood, and then seal it with the resin/fiberglass treatment. Even if you seal top and bottom surfaces of the MDF, I would be afraid that the moisture that is typical in most darkrooms would find its way in through small cracks or joints in the bottom surfaces and eventually ruin the sink. Although it may cost more initially, I would bet that in the long term the treated plywood will be serviceable for much longer and therefore more cost effective.
I have a friend who built a sink for a college darkroom. It has been getting daily heavy use for over 20 years now and is still going strong. He used plywood - which I would prefer over MDF, but that sounds like it is done, and his coating was a spray on pickup truck bed liner - I don't know what you would call that in Ireland, pickup trucks are far less common there, and I don't know about bed liners - but here is a link for a US chain that does this sort of work:
I would go one step further than using polyester resin. I would put in a few layers of glass fibre matt too so if (when?) the wood finally rots away, you still have a sturdy and useable sink.
"People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.