Kitchen worktop joints - what's the best way to make them waterproof?

[no_...@thanks.com]

It's time to do a couple of mason's mitres (using a Unika jig) so I've
been looking around for opinions and seen arguments for/against using
colorfill, silicone, sanding sealer and slow-set polyurethane adhesive.
What's the most reliable way to seal the joints?

Also, is it worth using biscuits to help with the vertical alignment?

[harryagain]

<no_...@thanks.com> wrote in message
news:bvk6eb...@mid.individual.net...

You can buy steel clamps consisting of a long bolt to make the joint.
You need two clamps per joint.
You need a large drill to make the blind holes for the joint.
They work very well and allow a small degree of adjustment.
Before the clamps were available I used dowels for the job but the clamps
make it easier to be accurate and also pull the joint up tighter.

I have just used PVA glue in the past.

[fred]

In article <bvk6eb...@mid.individual.net>, no_...@thanks.com writes

>It's time to do a couple of mason's mitres (using a Unika jig) so I've
>been looking around for opinions and seen arguments for/against using
>colorfill, silicone, sanding sealer and slow-set polyurethane adhesive.
>What's the most reliable way to seal the joints?
>

If you have the time I'd say you want first to use sanding sealer or
thinned polyurethane varnish in repeated applications over a day to get
a good soaked in depth of water resistance. Then use the slow set poly
you mention or one of the double purpose sealants such as Plumbers' Gold
(both evilly sticky and an excellent sealant) when doing the
jointing[1].

Water will have years to attack so it's best to have 2 lines of defence.

>Also, is it worth using biscuits to help with the vertical alignment?

Absolutely and make an extra effort to seal the cuts for the biscuits
(more area for moisture attack) and fully back fill with sealant on
assembly.

[1] Ideally mask the finished surface near the edge before assembly as
it's a bugger to get off without solvents afterwards.
--
fred
it's a ba-na-na . . . .

[John Rumm]

On 08/06/2014 23:29, no_...@thanks.com wrote:

> It's time to do a couple of mason's mitres (using a Unika jig) so I've
> been looking around for opinions and seen arguments for/against using
> colorfill, silicone, sanding sealer and slow-set polyurethane adhesive.
> What's the most reliable way to seal the joints?

Ideally seal the cut end thoroughly first with something that can soak
right in and make it non absorbent. The use a generous helping of
glue/filler/sealer when assembling the joint. Cramp it up tight with the
dog bone connectors.

> Also, is it worth using biscuits to help with the vertical alignment?

Yes I normally do - it makes it easier to keep it all aligned while you
do up the dog bones. The alternative it to clamp a couple of bits of
scrap wood across the joint to maintain the top surface alignment.

--
Cheers,

John.

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[DerbyBorn]

>

Would anything that soaks in be liable to cause local swelling?

[John Rumm]

On 09/06/2014 15:31, DerbyBorn wrote:
>>
>
> Would anything that soaks in be liable to cause local swelling?

I would avoid water based things.... shellac sealer would be good, as
would a traditional oil paint or primer.

[stuart noble]

On 09/06/2014 16:16, John Rumm wrote:
> On 09/06/2014 15:31, DerbyBorn wrote:
>>>
>>
>> Would anything that soaks in be liable to cause local swelling?
>
> I would avoid water based things.... shellac sealer would be good, as
> would a traditional oil paint or primer.
>
>

Shellac needs but a whiff of anything alkaline (bicarb even) to become
totally water soluble. I'd go for a moisture curing polyurethane adhesive