<p>As a 3D printer operator, the first thought in my alleged mind is to use PVA, a type of (expensive) filament which is printed as support for complex models. The model is placed in a water bath and agitated, which dissolves the PVA, leaving a cleanly supported model.</p>
<p>PVA is also a component of white glue and yellow glue (paper and wood glue), but I've not tried to wash away dried glue of either type for any reason.</p>
<p>Additionally, hot glue is a similar product and I can attest from experience that hot glue will drop its bond when subjected to isopropyl alcohol. This may be the most effective method to accomplish your objective. A bulk purchase of glue sticks, deposited in your mold using a hot air gun for maximum thermal transfer will provide both the securing of the semi-spherical rocks as well as the exclusion of the concrete mix.</p>
<p>Even if you decline to use IPA to remove the hot glue, it will also fall free of the concrete and rock mix under the heat gun.</p>

CC BY-SA 4.0
2023-05-23T17:20:14.720Z
Some good ideas here . . .  this piece will be rather large (4" x 14" x 60").  The material I seek (the word "resin" is just a placeholder) will both hold the rocks in place and keep the concrete from reaching the walls of the mold - then be completely removable.  Do you do 3D printing commercially or ?
user16931
CC BY-SA 4.0
2023-05-23T19:28:32.080Z
For the last six years, it's been a hobby, but I'm tapering away as of late. The hot glue will certainly prevent concrete from reaching areas you wish to exclude.
fred_dot_u
CC BY-SA 4.0
2023-05-22T21:19:22.623Z
2023-05-22T21:19:22.623Z
fred_dot_u
<p>I am making a floating shelf of concrete, using a mold.  I want several edges to have smooth round rocks embedded in them with a bit of &quot;relief&quot; to reveal semi-spherical rocks.  Ideally I would build up these edges of the mold with a firm liquid resin using gravity to hold the rocks in place, then become firmer. Then I will pour the concrete.  Once the concrete is dry and removed from the mold, I'd like to wash away the resin to reveal the rock - now on the edge of the concrete.</p>
<p>I need to hold the rocks in place AND keep the concrete from forming out to the edge of the mold.</p>
<p>What material can I use to do this ? The color or clarity of the resin is not important as it will be washed away.</p>

CC BY-SA 4.0
2023-05-23T14:38:24.040Z
Does it need to be resin? What about something to hold the stones in place that could be semi-easily removed after the concrete sets like Plaster of Paris.  It seems like something water soluble may not hold up against wet concrete which by definition has a lot of water in it.
rebusB
CC BY-SA 4.0
2023-05-23T19:46:25.977Z
It does not need to be resin.  Plaster of Paris may do the trick - it will hold the rocks and be hard enough to resist the concrete.  Then I could remove it  (after the concrete is set) with a pressure washer  . . .  this might work well.  Thanks.
user16931
<adhesives>
I am looking for a hard set resin that can be washed away with water
user16931
# I am looking for a hard set resin that can be washed away with water

(Asked by: username_0 on 2023-05-22)

I am making a floating shelf of concrete, using a mold. I want several edges to have smooth round rocks embedded in them with a bit of "relief" to reveal semi-spherical rocks. Ideally I would build up these edges of the mold with a firm liquid resin using gravity to hold the rocks in place, then become firmer. Then I will pour the concrete. Once the concrete is dry and removed from the mold, I'd like to wash away the resin to reveal the rock - now on the edge of the concrete.

I need to hold the rocks in place AND keep the concrete from forming out to the edge of the mold.

What material can I use to do this ? The color or clarity of the resin is not important as it will be washed away.

**Tags:** adhesives

> **Comments:**
> **username_1**: Does it need to be resin? What about something to hold the stones in place that could be semi-easily removed after the concrete sets like Plaster of Paris.  It seems like something water soluble may not hold up against wet concrete which by definition has a lot of water in it.  
> **username_0**: It does not need to be resin.  Plaster of Paris may do the trick - it will hold the rocks and be hard enough to resist the concrete.  Then I could remove it  (after the concrete is set) with a pressure washer  . . .  this might work well.  Thanks.  

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## 1 answers

### Answer by username_2 on 2023-05-22. Score: 3

As a 3D printer operator, the first thought in my alleged mind is to use PVA, a type of (expensive) filament which is printed as support for complex models. The model is placed in a water bath and agitated, which dissolves the PVA, leaving a cleanly supported model.

PVA is also a component of white glue and yellow glue (paper and wood glue), but I've not tried to wash away dried glue of either type for any reason.

Additionally, hot glue is a similar product and I can attest from experience that hot glue will drop its bond when subjected to isopropyl alcohol. This may be the most effective method to accomplish your objective. A bulk purchase of glue sticks, deposited in your mold using a hot air gun for maximum thermal transfer will provide both the securing of the semi-spherical rocks as well as the exclusion of the concrete mix.

Even if you decline to use IPA to remove the hot glue, it will also fall free of the concrete and rock mix under the heat gun.

> **Comments:**
> **username_0**: Some good ideas here . . .  this piece will be rather large (4" x 14" x 60").  The material I seek (the word "resin" is just a placeholder) will both hold the rocks in place and keep the concrete from reaching the walls of the mold - then be completely removable.  Do you do 3D printing commercially or ?  
> **username_2**: For the last six years, it's been a hobby, but I'm tapering away as of late. The hot glue will certainly prevent concrete from reaching areas you wish to exclude.  

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