discoloration when casting in resin

[its_virgil]

Not arguing with you, and I understand your concery. Every cast I've done was sticky on the surface that touched the air but were always cured hard all the way through. I have had some that never cured but I think I altered the chemistry by adding the wrong kind of colorant or too much of it. Most of what I cast are snake skins and they always cure rock hard. I have 4 or five colored casting and the pens are as hard today as they were 18 months ago when I cast them. I have my system and it is working for me. I think once the resin cures, there is no uncuring. Not trying to convert anyone, just relaying what I discover so we can all have fun casting and I know that is what you are doing also. And you gave some really good information. Happy casting.
do a good turn daily!
Don

Originally posted by TomServo
<br />Don: my concern with the sticky surface problem, is how do you know the center is fully cured? I don't ever want to have a PR blank come back because it got mushy from skin oils or something normally harmless... The first couple i did, never hardened up fully (there's still a mushy blank in my box) and the pen was a little soft after i turned it.. The ones i put on my aqarium light (it's a bit warm up there) to cure are rock solid, and have stayed that way except when i hit them with DNA..

 

[GaWoodworker]

Originally posted by TomServo
<br />Don: my concern with the sticky surface problem, is how do you know the center is fully cured?

Fortunately, I have never had a piece that has not had a mushy center. I use the small amount of resin that remains after I pour as my guide to the state of curing. Leave it in a wax cup or pour it into an empty mold. If it is rubbery, I know it hasn't cured but if it is rock hard, the resin in my castings will also be rock hard.

To this point, I have not had a skin prevent curing. I have had them turn, but not hinder curing. Those from the Snake Den are safe, but I'm sure it is possible that other methods of sealing skins could have a coating that might cause defective curing. Sometimes the skins from the Snake Den are fairly oily as if they were newly preserved. I leave them out in the air for a week or so and they always dry out fine.

Your research was great. You provided a lot of valuable information that I found to be very helpful. Thanks for all the work you shared with this group!

 

[TomServo]

Thanks! it wasn't that hard to find, really.

One question: (for don perhaps) did the skins turn black when you coated them with epoxy, or later when you encapsulated with PR?

 

[its_virgil]

GaWoodworker,
The thinner the cast the longer it takes to cure. The small amount of left over resin will take longer to cure than your pen blank cast. Thin castings build up less heat. That's why the amount of catalyst used changes with the thickness of the cast...according to the directions on the can. It's not rocket science, but it is some kind of sciece. The sticky surface does not alter the curing time as far as I can tell.
Do a good turn daily!
Don

Originally posted by GaWoodworker
<br />

Originally posted by TomServo
<br />Don: my concern with the sticky surface problem, is how do you know the center is fully cured?

Fortunately, I have never had a piece that has not had a mushy center. I use the small amount of resin that remains after I pour as my guide to the state of curing. Leave it in a wax cup or pour it into an empty mold. If it is rubbery, I know it hasn't cured but if it is rock hard, the resin in my castings will also be rock hard.

To this point, I have not had a skin prevent curing. I have had them turn, but not hinder curing. Those from the Snake Den are safe, but I'm sure it is possible that other methods of sealing skins could have a coating that might cause defective curing. Sometimes the skins from the Snake Den are fairly oily as if they were newly preserved. I leave them out in the air for a week or so and they always dry out fine.

Your research was great. You provided a lot of valuable information that I found to be very helpful. Thanks for all the work you shared with this group!

 

[its_virgil]

Tom,
The ones that turned black turned after the resin was added. I think it is more the heat and the tanning chemicals, but as thick as that resin is, it must thin out when the heat starts because it can seep throug the smallest of cracks. When I've thought I've had the ends sealed with wooden plugs and sealed with CA, the stuff still has managed to leak inside the tubes. Maybe my epoxy coatings were too thin or had a breach in them. But, the skins from sdsnake.com have never turned dark...not once.
Do a good turn daily!
don

Originally posted by TomServo
<br />Thanks! it wasn't that hard to find, really.

One question: (for don perhaps) did the skins turn black when you coated them with epoxy, or later when you encapsulated with PR?

 

[GaWoodworker]

Originally posted by its_virgil
<br />GaWoodworker,
The thinner the cast the longer it takes to cure. The small amount of left over resin will take longer to cure than your pen blank cast. Thin castings build up less heat. That's why the amount of catalyst used changes with the thickness of the cast...according to the directions on the can. It's not rocket science, but it is some kind of sciece. The sticky surface does not alter the curing time as far as I can tell.
Do a good turn daily!
Don

I'm not sure I understand the point you are trying to make? Are you responding to one of the post about sticky surfaces or am I overlooking what you are trying to say?[8)]

 

[its_virgil]

GaWoodworker,
Maybe I'm confused. You said: Fortunately, I have never had a piece that has not had a mushy center. To me this means that all your centers are mushy, but I don't think that is what you mean because you began with the word Fortuanately.

You said: I use the small amount of resin that remains after I pour as my guide to the state of curing. Leave it in a wax cup or pour it into an empty mold. If it is rubbery, I know it hasn't cured but if it is rock hard, the resin in my castings will also be rock hard. My comment is that the thinner the cast or the thinner the resin thickness the longer it takes to cure. So, when the thin left over amount is cured, the real casing should have long ago cured. Thick = faster curing and thin = slower curing because of the heat.

You said:To this point, I have not had a skin prevent curing. I have had them turn, but not hinder curing. I thought I replied that the skins have not hindered the curing for me, they just turn black or dark and you can't tell what is in the casting.

You said: my concern with the sticky surface problem, is how do you know the center is fully cured? My response: the surface exposed to the air is always sticky(unmless you do something to prevent it). Why do anything to prevent the sticky surface for pen blanks...it will be turned away and end up on the floor. How do I know it is cured? It will be hard. I don't think it will cure partially i.e cure 3/4 in thick all the way around and leave 1/8 inch uncurred in the center. I have never turned a home cast blank that was uncurred in the center. If they seem to be a little pliable, I set them aside for a few days and they harden. I have had a few that never cured and I think that was due to the colorant I used that screwed up the chemical reaction and after three weeks it was still not cured. 99% of what I cast is cured with an hour or sooner and I turn it the next day. Have had no problems with uncurred centers.

I hope this helps and sorry about the confusion. We had two topics going in this thread....skins turning black and the sticky surface and curing.

Do a good turn ldaily!
Don

 

[Darley]

Originally posted by TomServo
<br /> except when i hit them with DNA..

Why would you use DNA on, with, in PR casting?

 

[Darley]

I find this site for people who are concern about PR sticky surface after curing, scroll down to 3/4 page and you have a product for it, but I my regards will not buy like Don say you turn it away

http://tinyurl.com/9vea3

 

[GaWoodworker]

Originally posted by its_virgil
<br />GaWoodworker,
Maybe I'm confused. You said: Fortunately, I have never had a piece that has not had a mushy center. To me this means that all your centers are mushy, but I don't think that is what you mean because you began with the word Fortuanately.

Do a good turn ldaily!
Don[/red]

Ahhh. I mistyped. I meant that <b>I have never had a piece that has had a mushy center.</b> One little <s>not</s> can make a big knot in my post

[:I]