Michael's casting resin..question

[curlymaplefan]

I have just tonight started to play with casting I think I am going to love it....

My question..because I am unclear... for a mold aprox..3/4x3/4x3-1/4
I mixed up lets say 2oz of resin or there abouts..how many drops of hardner do I need?? I put in 4 drops and mixed it for 1 min...it's been now drying for 90 min and it's not even close to getting hard..

room temp is about 60deg...

Thanks
Jim

 

[stevers]

Humidity will make a diff as well. I will normally put in 3 to 4 drops per ounce. When my shop gets down into the 50's and lower, it can go up to 6 or even 8 drops per ounce.
At the rate of MEKP you used, you may be looking at an over night cure. At 3 to 4 drops, mine usually takes 4 to 6 hours and some times more. The more can depend on if colors were added.
Hope this helps.

 

[gketell]

If you can apply heat that will help.

 

[Blind_Squirrel]

I use 3-4 drops per ounce of resin. I let my resin cure 12-24 hours. If after 24 hours it is still a bit soft I put it in a toster oven set to approx. 175 degrees for 10 minutes. Once the toaster oven shuts off I keep the blank(s) in the oven and allow everything to cool down.

Don't use an (toaster) oven that you use to cook food. Don't leave the oven unattended while it is turned on.

 

[sbell111]

If my blanks are still sticky after 24 hours or so, it usually means that it's too cold in the shop. If I move them to a warmer location, they'll likely be perfect after a few hours.

I'm not a fan of increasing teh amount of catalyst to make them cure faster. I believe that this makes for brittle blanks. I'm not sure if heating them in a toaster oven wouldn't do the same, so I don't use that method. For me, there's no downside to waiting a little longer.

 

[JohnU]

My last batch took almost 3 days to set with 5 drops per ounce, but my shop was cold so I wrote that off as the reason.

 

[stevers]

Originally posted by JohnU

My last batch took almost 3 days to set with 5 drops per ounce, but my shop was cold so I wrote that off as the reason.

I cast some stuff last summer that set in hours with 3 or 4 drops, then this winter I cast some with the same MEKP and it took 4 days to set. Temp can change everything.
The whole idea behind using a catalyst is to create heat. Poly resin would eventually cure on it's own, it would just take a "loooooonnnnggg" time. The MEKP creates a chemical reaction that causes heat and speeds up cure time.
Is that about right guys? I'm no chemist, but I get the general idea.

 

[MikeyMike]

Since the process depends on having a stable environment (temp and humidity), try this:

In an old cooler, drill a hole large enough for a power cord and run a small wattage lamp into the box. maybe a 15-watt? You would want to have a big bulb. Add about 8 oz of that blue crystal cat litter (silica dioxide) in a small tray.

Now, pour the pieces, place in the bottom of the cooler, turn on the lamp, close the lid. Wait.