sticky resin

[bklynpnk]

Hey guys...

Having a small issue with my resin, hoping all is not lost. I am using smooth-on 305 and adding about 2 drops of alumilite black dye in it. I am doing 2oz-2oz at a time. My product is coming out fairly good, except its tacky. Even the stuff I did yesterday is still faintly tacky. is there something I can do to help it out? am i doing something wrong? or could it be humidity thats slowing the dry time?

[mangozac]

2 oz is 28g, which is a large enough quantity that you shouldn't be having tackiness caused by mixing ratios. You're mixing by weight right? I'd be surprised if it was the humidity causing it, so I wonder if it's not a problem with the pigment? I know Paulson has mentioned issues mixing and matching some of the US brands before.

[bklynpnk]

Thanks for the tip on the pigment. I ran a full run just plain, and most came out dry, but a few pieces were sticky again. However, the items from the past couple days got a lot better. Perhaps because I am using a slower cure time resin? i dont mind the tackiness as long as it eventually goes away, lol.

[paulson games]

Are you using a spray on mold release? If you aren't waiting long enough for it to dry before pouring the resin it can cause the surface of the cast part to come out sticky.

When using the 305 for small parts it does take longer to set up than what their standard demould time lists. for 300 I give it a full half hour before demolding and for 305 it takes an hour.

I've had suff come out sticky or runny when it wasn't mixed completely or if I'd dripped some unmixed resin into the mold on accident. Simple way to correct that is to stir it better.

It may also be that the quantity of dye is too much, I use 1-2 drops for 16 oz of liquid or 4-5 drops for an entire gallon. That stuff goes a really long way so you can cut it down to almost nothing in the mix. Also make sure you add it to the A part (yellow container) not the b side.


I'd suggest is letting the mold release sit longer.
Make sure you are completely mixing the resin for a full 10-15 seconds.
Give it a full hour to cure before demolding and if all that doesn't help try cutting back on the dye as well.

[blind pig]

I've had this happen with too much pigment in the polyurethane or if I didn't mix or get the ratios just right.

Trial and error unfortunately. Try it without the dye and see if it happens.

How old is the resin?

[bklynpnk]

The resin and silicone are new, they came last week. I had another thought... The silicone is not smooth-on, but from jgreer. I recently read commemts that differences in company can effect things. Don't know the validity of it.. I may just need to play with the mix

[mangozac]

How precise are you being with measuring? Do you have accurate precision digital scales?

[bklynpnk]

I have a postal scale, so it is in ounces and gives me tenths.

[mangozac]

OK yeah that's way not accurate enough! 1 oz = 28.3g. You want 0.1g resolution, so I suppose the next best closest thing in ounces would be 100ths of an ounce (0.28g) resolution. I grabbed mine from eBay for cheap and they still work like a charm.

[bklynpnk]

well then, we have a winner then. Picked up a duel scale on ebay, can do .1g-500g or .01g-200g. That has to be the reason

[mangozac]

For the record 0.1g resolution is all I'd recommend - not only is it pretty difficult to actually pour out a quantity with better precision than that, but IMO 0-500g gives a better useful range for activities in addition to casting

[paulson games]

Wow, I feel silly I've never weighed out any of my resin... I eye ball everything using mixing cups with volume grades printed on the side.

[mangozac]

[blind pig]

I pretty much always weigh my resin, even though my job (Clinical Nurse) is really about mixing stuff by volume all day (and inserting the odd finger up a bum).

I find if I use measurements, it sometimes dosen't work and it is a bugger to clean the half-set gunk out of a mould.

[Lane]

How you measure should not matter as long as they are the right proportions.

Measuring by volume can be done quite accurately, easily within 1/4 ml, though on small volumes this could be significant.

Using a scale is only as accurate as the equipment.

What can be a problem is mixing your measurements. I had a resin that was 1:1 by volume but 100:87 by weight, no telling what it would have done if I had mixed 1:1 by weight.