PoP dryer re-visited

[Vodkaman]

So why air dry?

There are arguments for and against oven drying PoP molds. A lot of the TU PoP artists use oven drying, so it can

Edited March 18, 2009 by Vodkaman
word tabulations did not work, now its scruffy!!!

[redg8r]

That reminds me of a woodworkers lamp kiln. They work well when made and monitored safely.

Great article Dave, should work well for you.

[HJS]

Excellent study concerning speed of drying of PoP using different drying methods.

There's another issue I've been wondering about... and that is does drying time affect the final hardness of molds made from the PoP or DWP? Is slower drying (days) result in a harder mold than those force-dried in an oven (couple hours)? I think tyhis is pretty much what you were getting at with your study.

I know for a fact that when highway guys are pouring a new concrete deck on a bridge, they like the concrete to dry as slowly as possible to make it harder. During the warmer months they will go so far as to cover the setting concrete with wet burlap to slow the evaporation/hardening process... slower = harder. Boat hauls are sometimes made from concrete too and the setting concrete will be sprayed with a mist of water for days to slow the curing/drying process. All done to make the concrete haul harder.

Back to lure molds. Minor flaking of the lure cavity edges can sometimes be a big issue with my DWP 2-piece molds. Might slower=harder concept as it applies to concrete also apply to the drying time of DWP or PoP??? Hmmmm.....

[nova]

I knew there was another reason that I didn't feel comfortable setting my oven higher than 150. My concern was that I didn't want to "steam" the water and crack the molds.

I also take my molds out of the oven a couple of times and set them on a folded newspaper to draw out some of the water.

Great article Dave.

www.novalures.com

[Vodkaman]

"Gamers" web sites contain a lot of information and research into PoP, its variations and additives. This is a link to one such site: Construction Corner it further links other related information.

There is plenty of evidence that the mixing proportions are important. Too thin and the plaster mold will be weak. This link has a good section on mixing plaster: Hirst Arts Casting Page

This article has an interesting section on release agents: JAIC 1998, Volume 37, Number 1, Article 4 (pp. 35 to 47) see last para of section 3.2 and section 3.3.

This link contains a couple of comments relative to the oven drying weakness problem, but it is only one mans opinion: Re: ATM Does a *common plaster of Paris* tool deform when wet?

This link has a reference to mixing proportions by weight, which is the way I do mine. It suggests a ratio of 60 (PoP) / 40 (water), I actually use a slightly thinner ratio mix of 5/4 by weight. http://dspace.unimap.edu.my/bitstream/123456789/3305/4/Methodology.pdf

The third paragraph of this link: Re: ATM Plaster of Paris Tools suggests letting the mold cool down slowly in the oven, as removing the PoP cast to a cold climate could crack the mold. Seems a reasonable suggestion to me.

In summary, I could not find anything that says that oven drying PoP is a bad thing, other than keeping the temperature well below 150C.

I found a few references to reinforcing the mix with various materials such as wood pulp, hessian, etc. but more importantly, the mix has to be right, too weak a mixture is a bad thing.

Dave

Edited March 30, 2009 by Vodkaman