Disclaimer: Iâm not a professional woodworker nor a professional chemist. Quality
of such a project will most likely be better when done by someone with professional
experience.
Note: All product links leading to Amazon are affiliate links, this pages author
profits from qualified purchases.
This short blog entry is about the (hobbyist level) casting of a simple counter-top.
I always wanted to do some everyday life stuff with epoxy resin so the water damage
after a leaky water tap in a flat turned out to be the perfect opportunity for casting
something simple. After having some previous experience for epoxy resin for potting
electronics and sealing high pressure vacuum chambers - and as well as adding
a black layer of resin on top of a simple coffee table (as shown in the photograph
below) I decided to go with some - about 5 kg - of E45 epoxy (Affiliate link)
This might not be the best idea since this has a pot life of about 45 minutes - this
might be too short depending on what youâre planning and how youâre processing. If your
working fast enough - especially during the degassing steps - this epoxy is great
for food related stuff since itâs exactly the same material thatâs also used inside
of metal cans.
Epoxy provides a highly scratch resistant and chemically mostly durable surface
thatâs easy cleanable - just donât try to use Acetone.
Epoxy can be mixed with acrylic dye - but beware that not every dye is really suited
for epoxy. Some form clumps, others do not distribute evenly. Itâs wise to use
pigments (Affiliate link) that are specifically designed to be used with
epoxy. For vertical or highly inclined surfaces one should also use gel-coat resins
that have already included thixotropic agents that make them less viscous.
The sub construction
First - since the whole kitchen cabinet has been damaged - a substructure hat to be
built. This has been done using simple laminated pressboard boards. Theyâve been cut
to size using a circular saw. Since that wood is already laminated no surface
treatment was necessary. All parts have been connected using trunnels as well as
wood screws (Affiliate link). The basis for the countertop has also been
built using 20 millimeter wood as the other parts of the substructure.
Note the left hand side of the substructure looks different than the right hand
side since this is a dishwasher that getâs fitted. After applying a wooden board
to the front of course all frontpanels will look the same.
The sink was already present and should be continued to be used - at least as a
template - so the required hole has been cut using a milling machine (Affiliate link).
Since only 20mm wood has been used the part of the countertop carrying the sink has been
reinforced by steel sections (Affiliate link) that had been cut to
the required length - this would not be needed when using a thicker type of solid wood
or multiplex boards. As the old sink was already looking pretty bad it was
coated using acrylic sprays (Affiliate link) and two epoxy layers
on itâs own. After this coating has been applied the surface was again even,
perfectly homogeneous white and scratch resistant. The drainage hole has been
cut using a keyhole saw (Affiliate link).
Epoxy
Preparation of surfaces
Note that epoxy is really fluid and is entering any gaps or porous surfaces. First
one should seal all edges that should not be penetrated using silicone or acrylic
glue so theyâre totally tight. Surface such as untreated wood should be expected
to soak up much epoxy - one can counter that effect by simply using coated wood
as formwork during casting which is exactly whatâs done for epoxy resin tables.
In this case the epoxy is desired to be soaked up into the raw wood to seal up
and provide protection against water and vapors. Also keep in mind that epoxy is
not easy to remove so you should cover up nearby surfaces that should not be destroyed
or glued by the epoxy - and keep in mind that it gets soaked up by a huge bunch
of materials, itâs not wall paint.
In case of the countertop the space between the wooden surface and the tiling has
been filled with acrylic glue and tested to be tight. The surface was left uncased
and open towards the front. This means that excess epoxy is dripping down at the
edge which also means that one has to remove blobs during the first hours after
the pour that form on the bottom of the countertop and keep the front clear by
ensuring that epoxy is flowing over the edge at all positions. It also means that
one should of course cover the floor to prevent damage - donât plan to simply wipe
away overflowing epoxy from your floor - that wonât work.
Just as a last comment about surfaces: Keep them clean before pouring. Any dust
or particles on the surface will stay there and might lead to uneven casts.
Degassing using vacuum pumps
After previous experience with using epoxy without outgassing and heavy buildup
of bubbles this is the first time I really cared and thought to try out evacuation
to remove trapped air bubble from the resin before casting. This turned out to
work even better than Iâve imagined. On the previous table project bubble buildup
has been a major problem - one had to use a heatgun to remove them continuously
even hours after pouring. After degassing not a single bubble occurred. Outgassing
has been done at approximately 75 pascal using a single stage rotary vane pump
and a stainless steel - acrylic glass vacuum chamber. Note that the acrylic
glass extremely limits the abilities of a vacuum chamber (at least if I as a physicist
think about vacuum) but itâs really way enough to outgas resins or other workpieces.
A vacuum chamber and single stage rotary vane pump can be bought pretty low prices.
Itâs not totally necessary to outgas resin but itâs really a huge improvement in
handling quality as well as the result.
Because Iâve used a rather fast E45 epoxy resin system (Affiliate link)
I decided to first outgas all components before mixing them. Note that the hardener
is also highly hygroscopic - i.e. it tends to capture water vapor that lowers or
even stops itâs capability of curing. That sounds way worse than it really is - it
just means that you shouldnât let the hardener stay open for a longer period of
time in humid areas as well as it limits shelf / storage lifetime to about one
or two years. The hardener doesnât capture that much air though. The resin itself -
in this case Bisphenol A - captures gasses.
I first outgassed the hardener for about 5 minutes and then the resin for about 12
minutes as can be seen on the following video. I just put the resin into the
vacuum chamber, lowered pressure down to about 75 pascals and waited till no more
bubble have been visible.
After the outgassing step of all components theyâre mixed according to the manufacturers
ratio - try to stay as close as possible to the specified ratio. Adding more or less
hardener doesnât make your process faster or slower. Itâs a chemical reaction that
takes place - everything thatâs available too much simply wonât react and stay in itâs
original form. This means that missing the correct ratio of components just leads
to sticky or even fluid and less scratch resistant surfaces. Itâs a good idea to
use a simple kitchen scale (Affiliate link) to mix according to weights.
Itâs also really important to provide a good mixture - keep stirring the epoxy
and also scratch the walls and bottom of your mixing container till you donât see
any smearing any more. Also donât try to mix too much epoxy inside a too small
container or pour layers that are too thick - stick to the manufacturers instructions
that fit your epoxy system. This is required since the chemical reaction is exothermic
so the heat has to be transferred out of the resin during curing. The instructions
given by the manufacturer are calculated by reaction rate vs. thermal conductivity
of your epoxy. Donât try to cool down the epoxy too much though since that may
stop the reaction - even permanently. Usually epoxy cures best between 25 and 35
degrees Celsius - but again stick to the instructions of your manufacturer. If you
donât the resin might end up not curing at all or building bubble due to boiling.
Note that outgassing of the mixed epoxy (resin, hardener and pigments) lead to
the largest gas release and bubble formation. Because of this one should carefully
control pressure to prevent overflow - and as with any vacuum system prevent large
pressure changes - change pressure slowly but keep in mind that the mixed epoxy
has a pot time somewhat below the specified time of the manufacturer and that youâve
to pour it during that time. And keep in mind that heat transfer is also hindered
by the vacuum inside the chamber. Just keep the epoxy inside long enough to remove
all large bubbles - in the best case if youâre epoxy is slow enough wait till no
more bubbles are formed. Be careful when repressurizing the chamber to not spill around
your epoxy.
Donât be afraid of epoxy getting hot though - usually it should not heat above about
45 Celsius but if you make mistakes during mixing it might even reach temperatures
above 110 Celsius as can be seen in the image below in which too much non degassed
epoxy has been mixed - the boiling water vapor and gas bubbles lead to epoxy
foam buildup that expanded somewhat like Polyurethane was pretty strong in the end:
Pouring
After outgassing the epoxy can be cured over the flat, smooth and horizontal surface.
Donât try to do too much corrections using brushes or rolls - theyâre good to force distribution
over large surfaces like floors but usually you should let gravity drive the distribution
and evening of the epoxy to get best results. The following image shows an intermediate
stage after the first layer had been poured. At the end the epoxy layer is thick enough
to cover the sink as a whole - it looks like the sink is part of the countertop (images
will be uploaded soon)
Look for bubbles - in case of good outgassing there shouldnât be any. In case
bubbles occur they can be removed using a hot air gun or a gas burner by blowing
them away gently and letting the epoxy reflow into the hole again. You might also
be capable of bursting bubbles using the tip of a paintbrush.
If you desire a thicker pour of epoxy like it was desired in this project one
should cast in multiple layers. Again consult the instructions of your particular
epoxy to determine if one should cast a few hours later or after the hardening
has been completely finished. For the epoxy I used it didnât really matter if
one poured 4-8 hours or 2 days later.
Note that if you have to cover larger vertical areas itâs a good idea to use
silicic acid to reduce fluidity of the resin. Donât try to wait till it gets
sticky to distribute it using brushes or rollers - that wonât work. On German
silicic acid is called Kieselsäure and is available at specialized shops
like Breddermann-Kunstharze. Youâll
have to look up a local supplier though.
Marbling
Marbling a surface is pretty easy when using epoxy and acrylic sprays (Affiliate link).
Simply apply them in different colors with enough distance. Donât be shy - I was during
my first marbling experience on epoxy and it really looks catastrophic during the first
stages of the process but itâs really easy and works pretty well. Just make some stripes
and dots with one color, then take the next. The following was made with a combination
of white pigmented epoxy combined with silver, brown and gold spray for a different
project: