Hollow mold

[traceour]

Hey!

Thinking of casting something similar to this

I've made the mold in plywood, but any tips on how to make it "hollow" to make it lighter? Maybe place some cardboard tubes or similar!?
Does it need reinforcement if the walls are about 10cm?
Then what's best for sealing gaps in the mold?

 

[mexitegel]

Made a similar bench. Put in a piece of foam (Styrofoam) of suitable size while filling the concrete. Turned out great.

I didn't reinforce since there's no load to speak of.

Seal gaps with latex caulk.

 

[traceour]

Have made a similar bench. Inserted a piece of expanded polystyrene (Styrofoam) of appropriate size while filling the concrete. Worked out great.

I didn't reinforce it since there isn't any significant load to speak of.

You can seal gaps with latex caulk.

Thanks, good idea, we'll go with that

 

[traceour]

Made a similar bench. Inserted a piece of cellular plastic (Styrofoam) of a suitable size while filling the concrete. Turned out great.

I didn't reinforce as there is no load to speak of.

Seal gaps with latex sealant.

Btw, which concrete did you use?

 

[mexitegel]

Now I'm a little unsure about what I used for that one actually .

Either regular fine concrete or expanding concrete. With the latter, you are guaranteed a good result as it doesn't need vibrating; you just need to tap the form a bit to achieve an almost completely pore-free casting.

Fine concrete works well too, it just needs more vibrating and is harder to make as pore-free.

 

[traceour]

Now I became a bit unsure about what I actually used for that .

Either regular fine concrete or expanding concrete. With the latter, you get a guaranteed good result as it doesn't need vibing, it's enough to tap a little on the mold to achieve an almost completely pore-free casting.

Fine concrete works well too; it just needs more vibing and is harder to get as pore-free.

Hello again, do you think I need to cover it in plastic and spray with water, etc.? I was thinking of casting at work to avoid making a mess at home and I don't have the possibility to come every day to water it. Will it still be acceptable?

 

[mexitegel]

If you don't have the opportunity to water, definitely cover with plastic and water beforehand. Especially if you are going to cast now when it's this warm.

 

[traceour]

If you don't have the opportunity to water, definitely cover it with plastic and water beforehand. Especially if you're going to cast now when it's quite warm.

Ok, thanks for the response.