Archinect
anchor

casting concrete and plaster

nothere

Hi,

I am looking into techniques, tips and processes on how to make casts using either concrete and/or plaster.
would prefer concrete.

thanks for any advice,

H

 
May 16, 08 5:34 am
mdler

concrete is heavy....just remember that...

May 16, 08 12:42 pm  · 
 · 
PodZilla

Two tips from someone who tried this unsuccessfully last semester:

1. make sure your mold is super watertight. Plaster is just slightly thicker than water and will leak out of even the smallest cracks.

2. If you're going to use plaster, please make sure you buy Hydrocal or similar that's meant for casting. The cheap plaster of paris from Home Depot is extremely temperamental and has an extremely short work window. It'll cost a bit more but it will make your life a lot easier in the long run. Also, make sure it's mixed correctly. If it's too thin, it'll take a year and day to cure. If it's too thick, it won't pour into the mold and will set too quickly.

Good Luck!

May 16, 08 12:42 pm  · 
 · 
xtbl

what are you casting? is it for a model?

the couple of times that i did cast stuff in school, i always liked using pour stone. it's a fast-setting anchoring cement. if you build your formwork right it comes out really nice.

but yeah, it's heavy.

May 16, 08 1:11 pm  · 
 · 
snook_dude

You need to have a releasing agent which covers the form inwhich your casting. If your doing plaster, you can use "Wisk" the degergent
in the Liquid State. I have used it in casting relief medallions. In casting in plaster you also have to take care not to create bubbles in your plaster by stirring the crap out of it. Never lift your paddle out of the plaster. Lots of luck. Start Small and you will have alot better luck when you need to go big. Actually if you get this down, you can move onto casting Bronze....now that kicks arShe!

May 16, 08 1:12 pm  · 
 · 
binary

when i casted some counters for a bathroom this is how i did it

made a24"x24" form with formica for the sides and silicone for the corners.... i used a 3/4" tube and cut it at 45degrees to scrap the wet silicone and create a roundover for the edges

the form was 1.5" deep and i used 4 bars or rebar and 3 layers or drywall mesh

my form was upside down so i could get a smooth finish against the formica and no water marks...

make sure the mold/form is totally level and sturdy

i could barely carry a 24"x24"x1.5" slab..... it was heavy and had to carry it to the 2nd floor...

seal it also if you are using it in a wet condition.....


b

May 16, 08 1:14 pm  · 
 · 
nothere

thanks!

May 16, 08 1:40 pm  · 
 · 
treekiller

if the plaster casting leaks, throw some (unmixed) plaster powder at the gusher and it will stop leaking.

May 16, 08 3:48 pm  · 
 · 
PodZilla

Treekiller, great tip! could have used that a month ago...

May 16, 08 3:52 pm  · 
 · 
treekiller

to tint plaster, mix tempra paint or dry pigments into it.

May 16, 08 3:56 pm  · 
 · 
holz.box

packing tape makes a killer finish for concrete, fyi.

May 16, 08 4:02 pm  · 
 · 
invisiblecanook

If it is a small enough piece, rockite is the way to go. Build your formwork out of bass wood, and use paste wax as a release agent. Works every time. Plus with rockite, you can water it down to the consistency of ganache, and it pours real easy out of a cup.

May 16, 08 11:22 pm  · 
 · 
citrus.grey

I agree with the Rockite but I’d build the formwork out of Plexiglas, it's stronger than bass wood, cheaper, water tight, and it doesn't need a releasing agent. Another benefit of a plexi mold is that you can piece it together with a hot glue gun which means it comes apart easily and can be used again and again.

May 16, 08 11:51 pm  · 
 · 
sohrabzzz

دور لامپی پلیمری گروه تولیدی لوگوکات از جنس فوم فشرده میباشد

Jun 14, 20 5:16 am  · 
 · 

Block this user


Are you sure you want to block this user and hide all related comments throughout the site?

Archinect


This is your first comment on Archinect. Your comment will be visible once approved.

  • ×Search in: