Oldgreybeard
12th May 2015, 01:21 PM
Over the past 2 months Peter (_fly_) has been helping me - a beginner when it comes to casting pen blanks. After spending 2 hours yesterday, we were not able to determine the cause of my current problem.
Basically I am trying to cast clear water-slip inkjet decals. Process is
1. Prime tube using acrylic grey automotive primer (Tube was roughed up with 180 grit paper before spraying)
2. Spray 1 coat of white automotive acrylic lacquer
3. Print decal and spray 2 coats with 'rattle can' clear acrylic lacquer (White Knight brand from Bunnings)
4. Water slide decal and used wet close-cell foam pad to 'squeeze' out air bubbles
5. Cast with clear polyester resin at 55 PSI in pressure pot over night.
(Each step was allowed to dry before moving to the next step)
346883346884The problem is that the day after turning there were a couple of small (approx. 2mm sq) silver spots which appearded to be underneath the decal. The pen has been inside the house for 2 weeks since turning and finishing and during this time the silver patches have increased in size and are now 2 -3 cm sq, and growing.The decal does not appear to be effected. Peter had not seen this before and could not offer any suggestions. Our 'best bet' was possibly a reaction between the resin and the automotive lacquer, but we could not come up with any reason why this would be so. There are some small air bubbles seen using a loupe, but these appear to be above the decal and higher up in the resin than the silver blotches.
I had the opportunity to discuss this with Amos over the phone last night, but it was not something which he had seen and was inclined to go with our best bet of some sort of reaction between the primer, automotive white lacquer, White Knight lacquer, the decal itself or the polyester resin. But whatand how to resolve the problem?
The thumbnail image on the left is the actual size of the pen (1/2" diameter). The image on the right is about 8x magnified when the 'larger image' is view on my monitor. The pen is cast on a 7mm 'Slimline" tube. The gold blurr showing above the pen adjacent to the top silver patch is the pen clip.
One question which Amos and Peter asked was why did I cast under pressure? Simple answer is that I had just finished setting up the pressure pot (and vacuum) and wanted to try my first resin casting (Seemed like a good idea at the time.) It seems that casting under pressure was not necessary and leaving over night under pressure was also unnecessary.
My first thought was that the problem was an air bubble, but now I think not. The image on the left shows 2 stages of the progression of the problem -
Firstly the fault appeared after a couple of hours as a grey smudge (circled in red) and then progessed to silver spots which have grown into the areas circled in green.
The image on the right shows the top silver area from a side on angle and I do not see any evidence of a bubble, but it does appear as if there is some breaking down of the clear film of the decal and / or the automotive white acrylic lacquer. (circled in green)
There is no doubt that I have done some things wrong and I would appreciate any suggestions as to how to avoid the problem in my next attempt. Watching Niel's (Dai Sensei) video again this morning , I am reasonable confident the the mixing of the resing and casting using a resin saver mould is not the cause - 2% MEPK.
Bob
Basically I am trying to cast clear water-slip inkjet decals. Process is
1. Prime tube using acrylic grey automotive primer (Tube was roughed up with 180 grit paper before spraying)
2. Spray 1 coat of white automotive acrylic lacquer
3. Print decal and spray 2 coats with 'rattle can' clear acrylic lacquer (White Knight brand from Bunnings)
4. Water slide decal and used wet close-cell foam pad to 'squeeze' out air bubbles
5. Cast with clear polyester resin at 55 PSI in pressure pot over night.
(Each step was allowed to dry before moving to the next step)
346883346884The problem is that the day after turning there were a couple of small (approx. 2mm sq) silver spots which appearded to be underneath the decal. The pen has been inside the house for 2 weeks since turning and finishing and during this time the silver patches have increased in size and are now 2 -3 cm sq, and growing.The decal does not appear to be effected. Peter had not seen this before and could not offer any suggestions. Our 'best bet' was possibly a reaction between the resin and the automotive lacquer, but we could not come up with any reason why this would be so. There are some small air bubbles seen using a loupe, but these appear to be above the decal and higher up in the resin than the silver blotches.
I had the opportunity to discuss this with Amos over the phone last night, but it was not something which he had seen and was inclined to go with our best bet of some sort of reaction between the primer, automotive white lacquer, White Knight lacquer, the decal itself or the polyester resin. But whatand how to resolve the problem?
The thumbnail image on the left is the actual size of the pen (1/2" diameter). The image on the right is about 8x magnified when the 'larger image' is view on my monitor. The pen is cast on a 7mm 'Slimline" tube. The gold blurr showing above the pen adjacent to the top silver patch is the pen clip.
One question which Amos and Peter asked was why did I cast under pressure? Simple answer is that I had just finished setting up the pressure pot (and vacuum) and wanted to try my first resin casting (Seemed like a good idea at the time.) It seems that casting under pressure was not necessary and leaving over night under pressure was also unnecessary.
My first thought was that the problem was an air bubble, but now I think not. The image on the left shows 2 stages of the progression of the problem -
Firstly the fault appeared after a couple of hours as a grey smudge (circled in red) and then progessed to silver spots which have grown into the areas circled in green.
The image on the right shows the top silver area from a side on angle and I do not see any evidence of a bubble, but it does appear as if there is some breaking down of the clear film of the decal and / or the automotive white acrylic lacquer. (circled in green)
There is no doubt that I have done some things wrong and I would appreciate any suggestions as to how to avoid the problem in my next attempt. Watching Niel's (Dai Sensei) video again this morning , I am reasonable confident the the mixing of the resing and casting using a resin saver mould is not the cause - 2% MEPK.
Bob