# sealing grout covered foam rocks



## fullmonti (May 10, 2013)

I'm in the process of making fake foam rocks. I have read a bunch of thread about this & coating them with grout seems a good & favorite way to go. I had the impression you didn't need to seal them up unless they were under water. If under water seal with epoxy. 

I have the sculpting done & got some unsanded grout & did some color tests on scraps of foam. I notice the grout is very soft. In fact it rubs of with ease like chalk. Obviously that wont hold up. So what have I done wrong or what do I need to seal them up with? Or is there a better way to go all together?

Thanks
Jim


----------



## Samuraisid (Apr 24, 2012)

How long has the grout been curing, and how have you gone about it?


----------



## fullmonti (May 10, 2013)

I just today did a test for different color combos. While I was at it I thought I'd put some on a test sculpted piece of foam. I mixed it about like a thick paint & brushed some on a textured area. It dried pretty fast & I guess I was thinking it was done, but perhaps it takes some time to cure/harden?

I just went back & reread a couple threads. I forgot about adding the acrylic cement additive (Acryl 60) to strengthen the grout. Also saw were HX said he keeps the grout wet for a week or so to fully cure.

As you can tell this is my first time at this. I'm proud of my foam sculpting work & don't want to screw it up by doing the grout poorly.


----------



## oldlady25715 (Nov 17, 2007)

There are threads that discuss it's gotta be kept wet for about 30 days till the PH drops. Then it's cured and hard like cement.


----------



## Samuraisid (Apr 24, 2012)

We all make mistakes when learning. 

Im functionally oriented and cant do anything aesthetic. My first attempt at grout turned out well, but my sculpting left me not using the pieces.

I suggest applying grout in layers. Your consistency is great, but apply the first layer very thin and add thickness with each additional layer. You want the previous layer to be mostly dry before applying the next. However, using a spray bottle, apply a light mist to the surface before adding another layer of grout. This combination will allow the layers to bond together better.

You can use Titebond in place of the acrylic fortifier, this is what a lot of professionals do. I started using a Canadian product called WeldBond, after a long conversation with a fellow exotic animal enthusiast, who also happens to be a contractor. Weldbond is half the price of Titebond in my area, so just choose a product that fits your budget and pull up all the TDS. A lot of glues can be used to fortify grout/mortar.


The Grout will cure 70-80% full strength within the first 3 days, and cure completely within 7 days if mixed properly. You need to keep the entire thing soaking wet for the rest of the month for leeching. 

Buy pH strips at your local big box store in the swimming pool section. Cheapest area I have found for them. Take a measurement of the water and write it down. Let the piece soak in the water, changing water every couple days. Once the pH normalizes, its good to go.


----------



## fullmonti (May 10, 2013)

Thanks so much for all the info.

Couple questions though. I seem to remember reading some where the extruded sheets of foam do not absorb water? If so I have large areas of foam in the back that do not show, so these areas do not really need to be grouted? 

Also some of what I'm doing is large chunks of foam & when you say soak them there is no way they will do anything but float like a big cork.  here is a photo of an intermediate stage. Only thing I can think is to hose them down & cover them. How come when you use this grout on a tile job no one keeps that grout wet for any time at all, so why is it necessary for this? Not lazy just curious.

Thanks again
Jim


----------



## Judy S (Aug 29, 2010)

The type of "foam" may make a real difference in what you are trying to do...regardless of that-the foam is going to suck some of the moisture into the pores of the foam...and that has to be taken into consideration...that's why the advice for several thin layers is more successful--flaking off of the paint will happen with the humidity unless the paint layers are allowed to totally cure from the inside out....can you be more specific about the "foam"?


----------



## fullmonti (May 10, 2013)

The foam is just the 4x8' sheet (usually blue or pink) extruded insulation boards sold at building supply stores, nothing exotic. 

Really am curious why you can use grout a 1/4" thick in one application in a tile shower that is in high humidity & is wet often & not keep it wet at all to cure & it be fine. Again not lazy just want to understand what's going on.

While we talking about this, I have never seen were any one has said how much of the acrylic additive/fortifier or titebond to use, just to use it. Are we talking 5 or 10% of volume or 50 50??


----------



## skanderson (Aug 25, 2011)

to cover the foam in all my builds i dont use grout because of the problems you are encountering. instead i bought a pail of acrylic mortar from menards. it is sold in grey or tan and is used to cover up the foam insulation on exposed foundation walls. i have added acrylic paint to it to alter the base coloration and i always sprinkle some dry grout over it when it is wet to get better depth of color. they sell it in 1 and 5 gallon pails but the small size covers well. it is in the same section of home improvement stores as the extruded foam insulation. just an idea.


----------



## fullmonti (May 10, 2013)

Really would like to know the couple things I ask about please.

Also I was out tonight & went by Lowes & Home Depot & neither of them knew any thing about a acrylic mortar. Would like to hear more about that too. Brand name, how you apply it, how it cures or drys, does it need to be sealed etc.?


----------



## oldlady25715 (Nov 17, 2007)

You can mist/hand spray the grout in the AM and PM then cover in plastic instead of submerging in water. 

To do multiple layers it takes months to get a tank done. I think they look great when done though and can be coated in epoxy to get a shiny look.


----------



## fullmonti (May 10, 2013)

No one every said why in this application we needed to keep grout wet for 30 days, when you do not need to when using the same grout for a tile job. Is it so it will get harder or to dissipate toxins? Or some other reason all together?

Also how & how much to mix of the acrylic fortifier AKA Acryl 60. I have not been able to find it locally yet so I can't read the direction on the label. I'm guessing in this application you don't go by the directions any way?

I have read some of the dozens & dozens (many of which are years old & links & photos are no longer available) of threads about this & don't remember seeing this info.

Like I said I have spent a good deal of time sculpting the foam & don't want to screw it up on the last steps.

Jim


----------



## Azurel (Aug 5, 2010)

fullmonti said:


> No one every said why in this application we needed to keep grout wet for 30 days, when you do not need to when using the same grout for a tile job. Is it so it will get harder or to dissipate toxins? Or some other reason all together?
> 
> Also how & how much to mix of the acrylic fortifier AKA Acryl 60. I have not been able to find it locally yet so I can't read the direction on the label. I'm guessing in this application you don't go by the directions any way?
> 
> ...


I haven't ever used grout but I think from my reading you keep it wet to remove the high PH. You want it to be a more neutral ph so it don't create issues for your plants and frogs with the higher then normal ph of the enviornment your trying to create.

I could be misunderstanding what I have read.


----------

