finish for a wooden sink

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hi experts,

I am going to build a wooden sink from a hollowed out solid block of cedar.
i have had plenty of woodcraft experts tell me not to, i hear what they say and i am doing it anyway.
my question is this, i want to make the inside of the sink waterproof.
i have spoken to some epoxy manufacturers who have all been extremely encouraging in the use of epoxy as a waterproofing medium for wood, however, none that i have spoken to make a foodsafe product. i was also warned that hot water can warp the epoxy finish.
it absolutely has to be foodsafe and i would rather it be temperature stable too.
the majority of use will be food prep with the occasional butchers block needing cleaning or pan that wont fit in the dishwasher.
does anyone on FOG know of a product which will be suitable?
i am not fixed upon the idea of using epoxy, other products are also up for consideration.
i am toying with the idea of using polyx oil if i cannot find anything else.
please don't suggest i make it from another material, i am aware of the possibility that my sink will crack and split, i am taking other precautionary measures to help reduce the risk; and to be fair, if it splits or breaks then i have only lost a bit of time and a block of wood, it's really not that important in the scheme of things. i will just re-evaluate my options should things go a little awry.

i am in the UK so products need to be available here or legal to import.

thank you to anyone with potentially helpful information. 
 
Flex Seal clear. I am pretty sure it used to be, if not still is food safe. I used it in a similar application too what you are going for and it has held up for 2 years for me so far.
 
No experience here, but John's post triggered a (possible) concern.  Liquids and food stuffs going from the stove to the sink introduce a higher range of heat exposure (pasta water or hot oils/fats).  It may not matter if it's your house and you can control what gets dumped into the sink.
 
bnaboatbuilder said:
Self leveling bar top epoxies are one option. They should be food safe since bars serve food and beverages all the time. Honestly, cured epoxy is inert and poses no health hazards. Uncured epoxy far less so, and the hardener in liquid form is the main nasty part that people get reactions to more than the resin itself. Epoxy dust from sanding is also bad for your lungs. Once epoxy has cured, not much else to it. Sink water will be about 120 F on average. I know here in the U.S. most water heaters are usually set at peak of about 130 F.

You can also use a marine varnish, 3 coats minimum, as many as you want beyond that. That will add additional waterproofing. Let it be known, no epoxy is truly waterproof, it's just that the water migration is so small over such a long time that for all intents and purposes, they say it's waterproof.

I would say that coating ALL surfaces (top and underside) would help prevent cracking over the long haul. The dryer the cedar the better. Cedar will soak in a lot of epoxy the first 2 coats if rolled or brushed on. Again 3 minimum maybe 4 coats to waterproof.

Both epoxy and varnish do scratch a little so don't expect it to be a perfect finish all the time.
Click to expand...

thanks for the info, do you mean varnish over the epoxy?
i was also pondering on how one might deal with vertical sides, perhaps set one side at a time?
will epoxy adhere to hardened epoxy? what i mean is: if i were to say set the bottom of the inside and leave it set, would a pouring onto one of the sides then adhere at the joint or would it be a weak point subject to water ingress?
point noted about the outside, i was planning to completely seal the wood all round as part of the process, it's nice to hear my thinking is sound in this respect.
being a boatman, are there any products you would recommend which would not soften in high temperatures, given that boats usually operate in cold water there is not normally call for them to operate under higher temperatures.

i enjoyed reading your response, it fueled further enthusiasm for my project. thank you.
 
Angelo said:
Flex Seal clear. I am pretty sure it used to be, if not still is food safe. I used it in a similar application too what you are going for and it has held up for 2 years for me so far.
Click to expand...

i shall do some research into this product, thank you for the first hand experience and recommendation.
 
RKA said:
No experience here, but John's post triggered a (possible) concern.  Liquids and food stuffs going from the stove to the sink introduce a higher range of heat exposure (pasta water or hot oils/fats).  It may not matter if it's your house and you can control what gets dumped into the sink.
Click to expand...

good point...
i think with regard to water that it will not go much above 100 degrees anyway (as long as products can hold that heat) no matter what you do with it... in a domestic setting anyhoo.
with regard to pans etc, you raise a good point and one i shall have to bear in mind and educate others in the house, i hadn't thought about that until you mentioned it. thank you for raising my awareness.
it is in my own house, so a bit of collective savvy should help preserve it...
 
System Three S1 penetrating epoxy.https://www.systemthree.com/products/s-1-clear-penetrating-epoxy-sealer
Don't know if its available in the UK.
You need penetrating type to prevent flaking. Kitchen sink gets more harsh treatment than bar top.
I was told by a boat builder (I can NOT independently confirm) that its food safe when cured. It was used, among other things, to seal wooden water storage tanks.
Being penetrating type it is very thin (consistency of diesel fuel) and soaks in quick and deep into wood. It will likely penetrate entirely through your cedar. Might require several applications. It makes wood water resistant in and out. It also takes quite some time to cure (more than a day) and it stinks!
You need to ask the manufacturer about its food safety.
 
Svar said:
System Three S1 penetrating epoxy.https://www.systemthree.com/products/s-1-clear-penetrating-epoxy-sealer
Don't know if its available in the UK.
You need penetrating type to prevent flaking. Kitchen sink gets more harsh treatment than bar top.
I was told by a boat builder (I can NOT independently confirm) that its food safe when cured. It was used, among other things, to seal wooden water storage tanks.
Being penetrating type it is very thin (consistency of diesel fuel) and soaks in quick and deep into wood. It will likely penetrate entirely through your cedar. Might require several applications. It makes wood water resistant in and out. It also takes quite some time to cure (more than a day) and it stinks!
You need to ask the manufacturer about its food safety.
Click to expand...

awesome, thank you for your help.
it sounds quite an interesting substance.
i shall contact the manufacturer to see if it is foodsafe, heat tolerant and available in the uk.
i like the idea of it penetrating the wood completely, that sounds like a perfect solution; almost as if one is plasticising the wood fibres throughout.
 
P.S.
There are other epoxies similar to S1, I used S1 because it was recommended by a professional. The keyword is penetrating epoxy. They are often used to stabilize rotten wood (another search criteria). Keep in mind that unlike regular ones they contain solvent to reduce viscosity and facilitate penetration. As a result they shrink when cured, not much, ~50% or so. Tested it myself by placing small amount into a test tube and letting it cure.

Here is a good link:http://lumberjocks.com/topics/46168
You can contact shipwright, he's still active on that forum. Check his work while at it.
 
You can cook an egg on a car bonnet/hood, so maybe a lacquer or 2-pack paint is food-safe?

After sanding and sealing the epoxy one could spray a clear 2-pack onto it or a lacquer.
I use deBeer which is a automotive 2pack, but I have not sprayed it over epoxied wood in a long time.
Lacquer has been used over a bunch of asian gear... (Bowls, plates, utensils) from "time-dot" 1.

We had a fellow at work that had a rare poisoning induced disorder. I think it was palsy??
They sent a person to watch his every move for a while.
He would take water out a 'sink' to make tea with like clockwork, and the water contained amines from an epoxy coating, even though the sink was filled with polished water.
The amines were playing havoc with him.

Personally I like epoxy, but I would be look at finding a lacquer for being foodsafe and dismiss the epoxy.

We should keep in mind that water is called the universal solvent for a reason.

No one has ever seen water change in a new testament sense where the atoms and molecules must become different. It needs to have something added to it, or be put up against something for the molecules to diffuse/absorb into the water, or collect gasses from the air.
Red water can be kept in wooden vessels for a long time, but it not end-grain wood. It is oak.
The liquid will only change from exposure to the wood or from the air.
Therefore taking a Kosher kitchen approach, and using a separate sink for food might make sense.

I am totally fine with people knowingly poisoning themselves with stimulants, depressants, hallucinogenics, psychotics...
Unknowingly poisoning one's self is something one should knowingly try to avoid.
So I would trust no one on how safe cured epoxy is. I would only trust an MSDS or some verifiable testing.
It it was a tub or hand or foot washing basin I would not hesitate, but a food sink you want to be sure.
...

If it was a raised bowl, then lining the inside with copper sheet/foil could be done. If you want wood exposed on the inside that approach will obviously be a fail.

1: "Time dot" Australian expression meaning the beginning of time just when time started and moved from zero, but before it hit an integer or natural number year.
 
Interesting project, if/when you complete it please update us on the process and results. I have no experience with such an application but I'd be considering the possibility of fiberglassing the surfaces for added strength. But like I said, your situation isn't something I'm familiar with.
 
Paul G said:
Interesting project, if/when you complete it please update us on the process and results. I have no experience with such an application but I'd be considering the possibility of fiberglassing the surfaces for added strength. But like I said, your situation isn't something I'm familiar with.
Click to expand...

^Nice^ mention...
Some of the thin tight weave fibreglass cloth is almost transparent when resined/epoxied up... Like a surfboard.
 
Holmz said:
Lacquer has been used over a bunch of asian gear... (Bowls, plates, utensils) from "time-dot" 1.
Click to expand...
Lacquer on asian lacqerware has little in common with lacqer you buy at a hardware store.

There is a number food grade FDA approved epoxies that meet NSF/ANSI toxicology standards. You just need to find out whether the one you use meets those standards.

Personally, I would not worry about it too much. You are not eating from the sink. If you worry about washing food there, then you should worry about any non-food grade surface you touch, as you might transfer toxins via your hands.
 
Paul G said:
came across this website today from an article in woodshop news magazine. While not a sink, certainly similar issues to deal with.
http://www.nkwoodworking.com/wood-bathtubs/
Click to expand...

thank you for the link, i have sent them a message and a link to this page, just wait and see what response i get and if they are will to divulge their process (fingers crossed).
 
Paul G said:
Interesting project, if/when you complete it please update us on the process and results. I have no experience with such an application but I'd be considering the possibility of fiberglassing the surfaces for added strength. But like I said, your situation isn't something I'm familiar with.
Click to expand...

i will indeed record the process involved, i don't anticipate an easy ride and i expect to learn a few things along the way...
well, i live in hope that i do anyhoo...

fibreglass seems like a fair solution, however i want the finish to really pop rather than be muted because of the matting.
 
bump said:
Paul G said:
came across this website today from an article in woodshop news magazine. While not a sink, certainly similar issues to deal with.
http://www.nkwoodworking.com/wood-bathtubs/
Click to expand...

thank you for the link, i have sent them a message and a link to this page, just wait and see what response i get and if they are will to divulge their process (fingers crossed).
Click to expand...

That would be surprising if they did. Seems almost a trade secret at this point.
 
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