I have an old Commodore 64 "dirt brown" case I'm going to treat in the next few days. I'm going to do one half using the Xanthan Gum/glycerine (Loren's recipie) and the other using Arrowroot.
Just an update on this.
Well, things haven't gone quite as planned. Firstly, the UV blub I had arranged to get from someone else turned out to be infra-red, not UV (duh!). That being the case I looked for a florescent bulb (with holder) but this was going to come to well over $100. Given things are tight right now financially, I couldn't justify that.
Ok, so I fell back on the good old NZ sun. The good old UNRELIABLE NZ sun. Not too much UV gets through when the sky is covered with thick clouds and it's raining occasionally. Some de-yellowing has occured on the Commodore case but not a lot happened in the gloom of yesterday. I'm looking to buy a UV source off our local auction site, so I should have one in the next few days or so.
One of the purposes of this particular trial was to see for myself the difference between Xantan gum and Arrowroot in ease of paste production and effectiveness.
I used my own Arrowroot reciepe and Lorne's modified Xantan gum one.
I found both pastes to be easy enough to make up. I found timing in relation to blending is important with the gum, just as timing in relation to heating is important for the Arrowroot. I tried Lorne's 5 seconds for the Gum but found I actually needed longer to mix it. In the end though, it does form a good paintable paste, although less thick that the Arrowroot. I found with these trials that if the Arrowroot is too thick initially good vigourous stirring when the activators is added, indeed thins it to a nice paste.
With only 6% H2O2 I found almost no foaming at all when I added dissolved Oxy to the Gum Mixture.
There is a big difference between the two pastes as regards drying out. The Arrowroot dries out fast and "sets" on the case in large flakes (as Lorne also observed). The Gum/glycerine takes a lot longer to dry out and seems to remain sticky. Whether or not activity is occuring underneath the Arrowroot flakes is not known.
i'm supposing some activity must occur as my previous cases dried out in the same way after about 20-30 mins. I reapplied from time to time but the total time "wet" then was probably no more than 2-3 hours. This may have been enough to do the job under the strong UV levels in the sun (well over 100x stronger than most UV tubes) but I would doubt it.
Anyway, yesterday I reapplied both the Arrowroot and gum/glycerine paste every 3 hours or so. As I said, not much happened due to gloomy light and the odd shower. There was a slight de-yellowing though with no noticable difference between the two paste mixtures.
Today the sun is out and I've made one (and only one) application on the "only sightly-deyellowed" case. I'm not going to re-apply today. I want to see if there is any noticable effect in de-yellowing between the gum and the paste. I wasn't going to do this "drying" comparison today..I was looking for just a straight efectiveness comparison. However, I'm out of paste and Hydroxide to make it with. (I used a lot of my RX-8000 yesterday trying to get the final streks of yellow out of that too), so I just had enough for one more go with the C-64.
My hypothesis is that the Arrowroot paste needs more applications that the Gum/glycerine paste to be as effective under sunlight. If at the end of the day the Gum/glycerine case is considerably less yellow, it will support that hypothesis. If not, perhaps they BOTH need reapplication frequently when outside.
Tez