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View Full Version : Gypsum - a warning...



Denzark
04-26-2011, 04:01 PM
Herewith something that may save you a lot of time.

Ages ago I got from my FLMS a 1:35 scale model of a ruined church, made by a czech firm. This easter I have been in terrain mode, so hoiked it out. I noticed that it said it was made of gypsum, and the dodgy czech-english translation left me unsure what this is.

Mistake 1: I thought it was resin, so prepared it with a good soak in a soapy tub to get the release agent off.

As this seemed to stay really damp when left under direct light for 2+ hours, I put it in the airing cupboard overnight.

The next day it still felt damp. I then put it in my top oven, with the main oven on gas mark 6. For another good hour. The stuff actually steamed!

I trimmed a couple of windows out - the constiuency is like wet clay. I then went to fix together using my favourite gorilla glue. Being impatient I wanted it done fast, hence super glue. It seemed super absorbent and wasn't all that good.

This is where I realised mistake 2. After it didn't seem to work, and finding my GF9 curing spray (which hisses like a psycho cat and would be capable of gluing the Gods themselves together) was empty, I looked up Gypsum on wikipedia. And I am here to tell you we sometimes know it as Plaster of Paris!

No wonder it feels damp! Bloody Plaster of Paris! the detail is good. However, I have resorted to a coat of PVA to try and cure it so will fill you in afterwards. FYI, PVA is sufficient for PoP but you may want a 2 part epoxy for a real tight bond. The Gorilla works but takes a bucketload.

I may post pictures if it comes out well, but hey, I've done this so you don't have to.

Lesson identified: Make sure you know what is in the box when you buy from crazy foreign companies where English is not the first language!

Firebird
04-26-2011, 04:30 PM
omg lol.... Why didnt you look it up online of what it was made of before you bought it?

Anyways Good story :)

Denzark
04-26-2011, 04:44 PM
The power of impulse buy!

JxKxR
04-26-2011, 04:52 PM
DAMN YOU IMPULSE BUYING!!! Thanks for the cautionary tale Denzark.

Tynskel
04-26-2011, 05:44 PM
Don't mess with a geologist!

Gypsum:
CaSO4•2H2O
Monoclinic
vitreous, gray-red, to clear, fibrous.

Here's the best part: when you reach 95C the structure transforms to polymorph of anhydrite (CaSO4).

But gypsum is a crucial ingredient in plaster of paris.
When you cooked it, your were on your way to making your own form of plaster.

Brass Scorpion
04-26-2011, 05:59 PM
Gypsum is a mineral that is also in what is commonly called "drywall". Gypsum is a common English word, one can hardly blame the manufacturer, "foreign" or not. Tip of the day: when confronted with new words, it's always a good idea to look them up. There must be dozens if not hundreds of free online dictionaries.

Tynskel
04-26-2011, 06:16 PM
it is decent as a drywall. But phyllosilicates are better, due to their hydrous structure (•8H2O or more sometimes. Great for delaying fire spreading).

Deadlift
04-27-2011, 04:15 AM
You lot and your big words trying to sound all knowledgable lol. At the end of the day is a fuc*king funny story that had me rolling with laughter. Thank you :)