# How to get a very smooth concrete mold_headstone



## tearitup (Jan 4, 2015)

Making a pet headstone / grave marker.
Planned on using the method of fixing ~ 1/8 in. thick letters in the bottom of a plastic pan, then pouring in the concrete.
Figured using a "sand topping mix" that doesn't have aggregate might work better, for getting in between parts of the letters (like middle of a 'P').

I've pour lots of slabs, etc. Even w/ "jigging" the concrete to get bubbles out - next to forms - you usually have way more voids from air bubbles than you'd like on a grave marker.

What's the best technique(S) to get all the bubbles out, where the concrete will meet the bottom of form pan (that will be marker's top surface)?

See example photo of how slick one guy got the surface of the marker, when poured into a plastic pan. Here's that link, but looks like he made it awfully soupy. https://www.youtube.com/watch?v=TZjvFQQWmSI

Making concrete or mortar mix *too "soupy"* reduces its strength quite a bit, but maybe that's one of the only ways to get it smooth at the bottom of a form?

? Maybe using cool water to mix it, then pouring only enough to barely cover the letters on form's bottom.
? Then use a small stick to work all air out of the concrete layer that's right against the form bottom? Then add rest of concrete?
? OR... After adding just a little concrete, repeatedly shake & tap the form on the ground - plus the other techniques I mentioned?


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## SeniorSitizen (Sep 10, 2012)

Rockite Kwixset is what I would use rather than a concrete or a portland cement grout mixture. Closely follow the manufacturer's mixing recommendations to get the correct pancake batter pouring viscosity.


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## oh'mike (Sep 18, 2009)

Concrete counter top makers use a vibrator to shake the form--working the mix around and fulling filling the form.


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## tearitup (Jan 4, 2015)

Thanks.


> Rockite Kwixset


* Never heard of that - in the South. 
Looking at Rocktite's site, no distributors or retailers listed in my area.

Either way, the mfg calls Rockite Kwixset an "exterior anchoring & patching cement."

I didn't find any specs on max thickness they recommend. Most of the "patching cements" aren't recommended for say, 2.5 in. thick - as I'll be using.

I believe other brands have similar similar products, but they're quite expensive. But I could check some out.

* oh'mike - just to clarify, what does "_and fulling filling the form_" mean?


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## SeniorSitizen (Sep 10, 2012)

The last Rockite I purchased was at Lowe's in a paper bag. It wasn't the Kwikset. I have a door stop made of some left over and I'll try to get a picture of it today sometime.


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## concrete_joe (Oct 6, 2014)

you can use mortar (bag) and add some portland to get some extra strength. a more soupy mix is what gets into the small pockets to make things smooth (w/o having correct vibrating table or vibrating tools).

you might try a 4:1 mix of mortar to portland to see how that sets. however, you'll likely be buying way to much stuff for the one small mix you need.

as mentioned, look for concrete mix (bag) for countertops. a local cememt company may also be able to get you a free sample for your "project", etc.


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## tearitup (Jan 4, 2015)

> last Rockite I purchased was at Lowe's


I don't find Rockite (brand) on Lowes web site & didn't see in local store. Do you see it?

* Concrete joe - yes, buying various bags of materials would be expensive.
Once a little (of what ever I use) is in the form (pan), may use a vibrating palm sander under the pan, along w/ tapping a rubber hammer. 

It's not a concrete vibrator, but there's very little surface area - or depth - to get air off the very bottom. Don't care if some bubbles are on the sides or bottom side of the marker.


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## SeniorSitizen (Sep 10, 2012)

IF you can't find Rockite Kwixset the subject is rather moot but in case you do at some point later I'll post the picture anyway.

This is regular Rockite and not Kwixset for outdoors, although this has been outdoors for several years but the surface showing has been down and not exposed to the elements as much as an upward surface. 

It was the remaunder of a job and poured into a plastic tub ( cool whip ) or some such container. It shows detail very well and is about the surface texture 400 grit sandpaper.


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## Canarywood1 (May 5, 2012)

What you use for the form is the key to how smooth it will turn out, as to removing all the bubbles good luck with that, stripping the form as soon as possible and using a slurry or grout to fill the voids is what contractors do.


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## concrete_joe (Oct 6, 2014)

a basic square? the melamine boards make smooth. plastic containers make smooth. 

complex shapes are likely silicone molds that peel away.


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## ChuckF. (Aug 25, 2013)

There are a few websites dedicated to DIY concrete kitchen counters. They recommend the right mixes and stuff to build the forms from.


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## joed (Mar 13, 2005)

Use your orbital sander as a vibrator.


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## tearitup (Jan 4, 2015)

Thanks.
yes - I'd thought about my vibrating sander (my rotary, elliptical is too smooth).
I watched some clips - "make a concrete countertop, sink basin," etc.
Maybe it was the type mix they used, but even w/ commercial vibrators, there were a fair # of air pin holes.

Most filled holes later w/ slurry that several said was only portland & water (or latex bonding agent). But for exterior, fully exposed application, I wonder how durable pure portland would be? It's actually not intended to be used by itself (AFAIK).

Sure, for concrete out of the weather, filling holes w/ portland slurry & then sealing is fine.

Some companies make "counter top mix" concrete, but I've not found locally (yet). Supposedly designed to mix to higher slump (thinner) than typical, w/o hurting strength. 

Part of the idea is, thinner material allows air to escape easier. Only price so far was Lowes ordering - $16 / 80#. Yikes!

But I may do a test - small container. Put in only 1/4 to 3/8 in. at 1st.
Use a dowel or end of a small stick & tamp the entire surface well, and vibrate. Then pour in some more. See how that works on air bubbles.


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## Bondo (Dec 8, 2007)

tearitup said:


> Thanks.
> yes - I'd thought about my vibrating sander (my rotary, elliptical is too smooth).
> I watched some clips - "make a concrete countertop, sink basin," etc.
> Maybe it was the type mix they used, but even w/ commercial vibrators, there were a fair # of air pin holes.
> ...


Ayuh,.... Use an old paintbrush,....

For rubbin' out the surface, 'n fillin' in any pittin', use either straight up portland, or bagged hyd. grout,....


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## Canarywood1 (May 5, 2012)

tearitup said:


> Thanks.
> yes - I'd thought about my vibrating sander (my rotary, elliptical is too smooth).
> I watched some clips - "make a concrete countertop, sink basin," etc.
> Maybe it was the type mix they used, but even w/ commercial vibrators, there were a fair # of air pin holes.
> ...


 


You can get away from using a lot of water to produce a high slump mix if you can buy Sikacrete in your area, it's a self consolidating concrete that uses super plasticisers to achive the high slump for what your trying to do, you also don't need to viabrate it, it will just flow into place with very little help from you.


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