{"id":9177,"date":"2024-01-08T01:00:00","date_gmt":"2024-01-08T01:00:00","guid":{"rendered":"https:\/\/uplastech.com\/batch-to-batch-colour-shift-pvc-extrusion\/"},"modified":"2026-11-08T08:10:50","modified_gmt":"2026-11-08T08:10:50","slug":"batch-to-batch-colour-shift-pvc-extrusion","status":"publish","type":"post","link":"https:\/\/uplastech.com\/it\/batch-to-batch-colour-shift-pvc-extrusion\/","title":{"rendered":"A second batch of grey PVC trim that will not match: \u0394E 2.6 against a limit of 1.0"},"content":{"rendered":"<style>\n.upl-blog{font-size:17px;line-height:1.78;color:#1f2937}\n.upl-blog p{margin:0 0 18px}\n.upl-blog h2{font-size:26px;line-height:1.3;color:#0b2b33;margin:46px 0 14px;font-weight:700;letter-spacing:-.015em}\n.upl-blog h3{font-size:19.5px;color:#0d3b47;margin:28px 0 10px;font-weight:700}\n.upl-blog ul,.upl-blog ol{margin:0 0 20px;padding-left:22px}\n.upl-blog li{margin:0 0 9px}\n.upl-blog figure{margin:0 0 34px}\n.upl-blog figure 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ul.cta-need li{color:#e4f0f2;font-size:14.5px;padding-left:18px;position:relative;margin:0}\n.upl-blog ul.cta-need li::before{content:\"\\2713\";position:absolute;left:0;color:#e07a1f;font-weight:700}\n\/* ==UPL-CONVERSION-MODULES-END== *\/\n@media(max-width:640px){.upl-blog h2{font-size:22px}.upl-blog table{font-size:13px}.upl-blog .cta{padding:24px}.upl-blog ul.conv-need,.upl-blog ul.cta-need{grid-template-columns:1fr}.upl-blog .problem,.upl-blog .steps,.upl-blog .conv,.upl-blog .checklist{padding:18px}}\n\/* \u5355\u7bc7\u9875\u9690\u85cf WhatsApp \u95ee\u5019\u5361\uff0c\u53ea\u4fdd\u7559\u5706\u5f62\u6c14\u6ce1\uff0c\u907f\u514d\u906e\u6321\u4fa7\u680f\u8be2\u76d8\u63d0\u4ea4\u6309\u94ae\u3002\n   \u6ce8\u610f\uff1aClick to Chat \u7684\u70b9\u51fb\u903b\u8f91\u662f\u300c\u95ee\u5019\u5361\u5143\u7d20\u5b58\u5728\u5c31\u4e0d\u8df3\u8f6c\u300d\uff0c\u53ea\u9760 CSS \u9690\u85cf\u4f1a\u8ba9\u6c14\u6ce1\u53d8\u6210\u6b7b\u94fe\u63a5\u3002\n   Code Snippets #9\u300cUPL single post: WhatsApp bubble jumps straight to chat\u300d\u8d1f\u8d23\u628a\u8be5\u8282\u70b9\u4ece DOM \u79fb\u9664\uff0c\n   \u4e0b\u9762\u8fd9\u6761 CSS \u53ea\u662f\u79fb\u9664\u524d\u7684\u89c6\u89c9\u515c\u5e95\u3002\u5220 #9 \u524d\u5fc5\u987b\u5148\u5220\u8fd9\u6761\u89c4\u5219\u3002 *\/\nbody.single-post .ht_ctc_chat_greetings_box{display:none !important}\n<\/style>\n<div class=\"upl-blog\">\n<figure>\n<img fetchpriority=\"high\" decoding=\"async\" src=\"https:\/\/uplastech.com\/wp-content\/uploads\/2026\/11\/2024-batch-to-batch-colour-shift-pvc-extrusion-hero.jpg\" alt=\"Real extruded plastic profiles and pipe on a production site\" width=\"1536\" height=\"909\"><figcaption>Real plastic profile extrusion production context. Photo: Pexels.<\/figcaption><\/figure>\n<div class=\"problem\">\n<p class=\"mod-h\">The problem<\/p>\n<p><b>Symptom.<\/b> A contractor fits a second delivery of grey PVC trim beside the first and sees a visible difference, measured at \u0394E*ab 2.6 under D65 against a contractual limit of 1.0.<\/p>\n<p><b>What it costs.<\/b> The mismatch is only visible once both batches are on the same elevation, by which point the first batch is installed and the whole run has to be replaced to keep one face uniform.<\/p>\n<p class=\"problem-promise\">This guide ties the shift to melt temperature and masterbatch dose, and gives the four controls that settle a colour dispute before installation.<\/p>\n<\/div>\n<div class=\"toc\"><\/div>\n<h2 id=\"agree-the-number-before-you-compare-the-parts\">Agree the number before you compare the parts<\/h2>\n<p>Colour is judged as \u0394E*ab against a retained master under D65 at 10\u00b0. Batch one read L* 72.4, a* -1.2, b* +3.1; batch two read 73.8, -1.5, +0.9, giving \u0394E 2.6 where the order allowed 1.0, and the b* drop shows degraded yellow pigment.<\/p>\n<table>\n<thead>\n<tr>\n<th>Zone 3 melt temp (\u00b0C)<\/th>\n<th>\u0394E*ab vs master<\/th>\n<th>Batches passing \u0394E \u2264 1.0 (%)<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>185 (specified)<\/td>\n<td>0.6<\/td>\n<td>96<\/td>\n<\/tr>\n<tr>\n<td>190<\/td>\n<td>1.2<\/td>\n<td>82<\/td>\n<\/tr>\n<tr>\n<td>195<\/td>\n<td>1.9<\/td>\n<td>48<\/td>\n<\/tr>\n<tr>\n<td>200 (drift)<\/td>\n<td>2.6<\/td>\n<td>18<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 1 - Melt temperature against colour difference and first-pass yield<\/p>\n<div class=\"callout\">Record which of these you are actually seeing before changing any setting. Two faults can look identical on the line and need opposite corrections.<\/div>\n<p><!-- upl-conv-v1 quickcta --><\/p>\n<div class=\"quickcta\">\n<p class=\"mod-h\">Need a fixed price for this profile?<\/p>\n<p>Send the cross-section drawing, material, cut length and annual volume. We will review die, calibration and tolerance, then return a written tooling and production quotation.<\/p>\n<p class=\"quickcta-act\"><a class=\"quickcta-btn\" href=\"https:\/\/uplastech.com\/plastic-extrusion-solutions\/\">Get a profile quotation<\/a><a class=\"quickcta-alt\" href=\"mailto:john@uplastech.com\">Email john@uplastech.com<\/a><a class=\"quickcta-alt\" href=\"https:\/\/wa.me\/8617717529949\">WhatsApp<\/a><\/p>\n<\/div>\n<h2 id=\"trace-the-shift-back-to-zone-3-and-the-dosing-unit\">Trace the shift back to zone 3 and the dosing unit<\/h2>\n<p>Typically, the shift traced to melt temperature drift, masterbatch dose error, regrind dilution, a missing retained master and metamerism under site lighting. Check the doser first: a 0.15% short dose of a 2.00% masterbatch moves L* by about 1.5 units.<\/p>\n<div class=\"steps\">\n<p class=\"mod-h\">A five-step diagnostic sequence<\/p>\n<ol>\n<li><b>Agree the master first.<\/b><br \/>Retain an approved sample and measure both batches against it under D65\/10\u00b0; without a master, \u0394E 2.6 is only an opinion.<\/li>\n<li><b>Read the zone 3 log.<\/b><br \/>Compare the melt temperature of both batches; a rise from 188 \u00b0C to 200 \u00b0C degrades organic pigment and drops b*.<\/li>\n<li><b>Check the gravimetric doser.<\/b><br \/>Confirm 2.00 \u00b1 0.05% masterbatch; a 0.15% short dose moves L* by about 1.5 units.<\/li>\n<li><b>Rule out regrind and lighting.<\/b><br \/>Verify 0% regrind on the visible face and compare \u0394E under both D65 and the site lighting to exclude metamerism.<\/li>\n<li><b>Run the melt-temperature trial.<\/b><br \/>Hold 185, 190, 195 and 200 \u00b0C and measure \u0394E; the 0.6 to 2.6 rise proves the drift, not the compound.<\/li>\n<\/ol>\n<\/div>\n<p>The chart below is a typical result from that measurement step. Use it to separate a design limit from a setting that can still be recovered.<\/p>\n<figure>\n<img decoding=\"async\" src=\"https:\/\/uplastech.com\/wp-content\/uploads\/2026\/11\/batch-to-batch-colour-shift-pvc-extrusion-chart3.jpg\" alt=\"A second batch of grey PVC trim that will not match: \u0394E 2.6 against a limit of 1.0: calculated response trend and an illustrative root-cause split\" width=\"1536\" height=\"909\"><figcaption>Figure 1 \u2014 Calculated response trend and an illustrative root-cause split. Values are engineering guidance for diagnosis, not a measured survey; confirm them on your own line before changing a drawing or a specification.<\/figcaption><\/figure>\n<h2 id=\"set-the-colour-controls-that-hold-between-batches\">Set the colour controls that hold between batches<\/h2>\n<p>Four controls hold the colour: \u0394E*ab of 1.0 or less under D65\/10\u00b0, masterbatch dosing at 2.00 \u00b1 0.05%, zone 3 melt at 185 to 190 \u00b0C, and no regrind on the visible face. Above 198 \u00b0C the organic pigment degrades and b* falls.<\/p>\n<table class=\"spec\">\n<thead>\n<tr>\n<th>Parameter<\/th>\n<th>Typical target<\/th>\n<th>What goes wrong outside it<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Colour difference \u0394E*ab (D65\/10\u00b0)<\/td>\n<td>1.0 or less against master<\/td>\n<td>Above 2.0 the trim is visibly different on one elevation<\/td>\n<\/tr>\n<tr>\n<td>Masterbatch dosing<\/td>\n<td>2.00 \u00b1 0.05 %<\/td>\n<td>A 0.15 % short dose shifts L* by about 1.5 units<\/td>\n<\/tr>\n<tr>\n<td>Zone 3 melt temperature<\/td>\n<td>185-190 \u00b0C<\/td>\n<td>Above 198 \u00b0C organic pigment degrades and b* falls<\/td>\n<\/tr>\n<tr>\n<td>Regrind on the visible face<\/td>\n<td>0 %<\/td>\n<td>10 % regrind dilutes pigment and lifts \u0394E by 0.8<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 2 - Colour controls that hold a grey PVC trim between batches<\/p>\n<h2 id=\"prove-it-with-a-melt-temperature-trial\">Prove it with a melt-temperature trial<\/h2>\n<p>Run a melt-temperature trial with one compound: hold zone 3 at 185, 190, 195 and 200 \u00b0C and measure \u0394E against the master. It reads 0.6, 1.2, 1.9 then 2.6, while the share of batches passing \u0394E 1.0 falls from 96% to 18%.<\/p>\n<table>\n<thead>\n<tr>\n<th>Field symptom<\/th>\n<th>Most likely cause<\/th>\n<th>Check that confirms it<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Second batch yellower \/ bluer<\/td>\n<td>Melt temperature drift<\/td>\n<td>Zone 3 log reads 200 \u00b0C instead of 188 \u00b0C<\/td>\n<\/tr>\n<tr>\n<td>Whole batch lighter<\/td>\n<td>Masterbatch dose short<\/td>\n<td>Gravimetric doser log shows 1.85 % not 2.00 %<\/td>\n<\/tr>\n<tr>\n<td>Match in the factory, not on site<\/td>\n<td>Metamerism under different lighting<\/td>\n<td>\u0394E changes between D65 and shop fluorescent<\/td>\n<\/tr>\n<tr>\n<td>Shift grows with regrind<\/td>\n<td>Regrind diluting the pigment<\/td>\n<td>Regrind ratio logged at 10 % on the visible face<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 3 - Matching the colour symptom to the process drift<\/p>\n<div class=\"myth\"><b>Myth:<\/b> \"A process adjustment will fix it.\" Once a design limit is reached, more tuning only adds cost and variation. Confirm the limit with a measurement, then change the drawing or the specification.<\/div>\n<h2 id=\"write-the-master-and-the-geometry-into-the-order\">Write the master and the geometry into the order<\/h2>\n<p>Write the master and the geometry into the order: a retained approved sample, \u0394E*ab under D65\/10\u00b0, the dose tolerance and conditioning temperature. Both parties measuring the same master turn a visible mismatch into a 2.6 reading, not an argument about the lighting.<\/p>\n<div class=\"conv\">\n<p class=\"mod-h\">Need the section checked before tooling?<\/p>\n<p>Send us the section and the installation conditions. We will review wall balance, tolerance and fixing detail, then return a marked-up drawing with a tooling quotation.<\/p>\n<p class=\"conv-lbl\">What to send us<\/p>\n<ul class=\"conv-need\">\n<li>Cross-section drawing with wall thicknesses<\/li>\n<li>Material and colour<\/li>\n<li>Installation temperature range<\/li>\n<li>Fixing method and run length<\/li>\n<\/ul>\n<p><a class=\"conv-btn\" href=\"\/plastic-extrusion-solutions\/\">Send the section drawing<\/a>\n<\/div>\n<h2 id=\"what-one-retained-standard-saves-over-a-project\">What one retained standard saves over a project<\/h2>\n<p>One retained standard protects the whole project. A facade takes 4 000 m of trim over several batches; holding zone 3 at 188 \u00b0C keeps \u0394E near 0.6, while a 12 \u00b0C drift shades a whole delivery before it is placed beside batch one.<\/p>\n<div class=\"callout\">Validate one change at a time and keep the measurement record. A supplier discussion backed by data is resolved in days, not weeks.<\/div>\n<div class=\"checklist\">\n<p class=\"mod-h\">Before you release this extruded profile<\/p>\n<ul>\n<li>A retained approved master sample is held by both parties<\/li>\n<li>\u0394E*ab limit and the D65\/10\u00b0 measurement geometry are specified<\/li>\n<li>Masterbatch dose and tolerance are written into the order<\/li>\n<li>Zone 3 melt temperature and its upper limit are stated<\/li>\n<li>Regrind is excluded from the visible face by specification<\/li>\n<\/ul>\n<p class=\"cl-note\">Write the measurement temperature and the tolerance into the drawing; most disputes are really about how the part was measured.<\/p>\n<\/div>\n<div class=\"faq\">\n<h3>Why does my second batch of grey trim look different?<\/h3>\n<p>Most often the melt ran hot. At 200 \u00b0C instead of 188 \u00b0C the organic yellow pigment degrades, b* falls and \u0394E*ab rises from 0.6 to 2.6 against a limit of 1.0.<\/p>\n<h3>How is colour difference properly measured?<\/h3>\n<p>As \u0394E*ab against a retained master using a spectrophotometer under D65 at 10\u00b0. Visual judgement under shop lighting is unreliable because metamerism can make two matching parts look different.<\/p>\n<h3>What \u0394E limit should I specify?<\/h3>\n<p>1.0 or less for a visible architectural trim. Above 2.0 the difference is obvious on one elevation, which is why a 2.6 reading usually means replacing the whole installed run.<\/p>\n<h3>Does masterbatch dosing matter that much?<\/h3>\n<p>Yes. 2.00 \u00b1 0.05% is the working tolerance. A 0.15% short dose shifts L* by about 1.5 units, which is already beyond most colour limits.<\/p>\n<h3>Can I use regrind on the visible face?<\/h3>\n<p>No. Ten per cent regrind dilutes the pigment and lifts \u0394E by about 0.8 on its own, before any temperature drift is added. Keep regrind to the core or a hidden face.<\/p>\n<h3>What should the acceptance clause include?<\/h3>\n<p>A retained master, the \u0394E limit under D65\/10\u00b0, dose tolerance, zone 3 temperature, and no regrind on the visible face. Both parties then measure the same numbers.<\/p>\n<\/div>\n<div class=\"cta\">\n<p class=\"cta-h\">Get a profile that holds its dimension<\/p>\n<p>Send us the profile section, the length and the service conditions. We will review die, calibration and tolerance, then quote tooling and production with a defined measurement method.<\/p>\n<p class=\"cta-lbl\">To get an accurate quote, send:<\/p>\n<ul class=\"cta-need\">\n<li>Profile cross-section drawing<\/li>\n<li>Material and colour<\/li>\n<li>Cut length and annual volume<\/li>\n<li>Service temperature and exposure<\/li>\n<\/ul>\n<p><a class=\"btn\" href=\"\/plastic-extrusion-solutions\/\">Request a profile quotation<\/a><br \/>\n<!-- upl-conv-v1 contact --><\/p>\n<div class=\"contactbar\">\n<p class=\"contactbar-h\">Prefer to talk it through first?<\/p>\n<p>Email <a href=\"mailto:john@uplastech.com\">john@uplastech.com<\/a> or message us on <a href=\"https:\/\/wa.me\/8617717529949\">WhatsApp +86 177 1752 9949<\/a>. Send a drawing, a sample or a specification and an engineer will reply.<\/p>\n<\/div>\n<p><!-- upl-conv-v1 trust --><\/p>\n<div class=\"trust\">\n<p class=\"trust-h\">Why buyers work with Uplastech<\/p>\n<p>ISO 9001, ISO 14001 and ISO 45001 certified. Founded in 2016, with injection moulding lines in Shanghai and an extrusion plant in Jiangsu. Moulding machines from 90T to 1100T and a maximum shot weight of 5100 g. Samples and a written quotation are available on request.<\/p>\n<\/div>\n<\/div>\n<div class=\"rel\">\n<h4>Continue reading<\/h4>\n<ul>\n<li><a href=\"https:\/\/uplastech.com\/extrusion-dimensional-drift\/\">Extrusion dimensional drift<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/extrusion-profile-tolerance\/\">Extrusion profile tolerance<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/profile-calibration-cooling\/\">Profile calibration and cooling<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/pvc-profile-weathering-colour\/\">PVC profile weathering and colour<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/pvc-window-profile-design\/\">PVC window profile design<\/a><\/li>\n<\/ul>\n<p><!-- upl-conv-v1 service --><\/p>\n<p class=\"rel-svc\">Ready to specify? See our <a href=\"https:\/\/uplastech.com\/plastic-extrusion-solutions\/\">plastic profile extrusion services<\/a> or <a href=\"mailto:john@uplastech.com\">request a written quotation<\/a>.<\/p>\n<\/div>\n<\/div>\n<p><script type=\"application\/ld+json\">{\"@context\": \"https:\/\/schema.org\", \"@type\": \"FAQPage\", \"mainEntity\": [{\"@type\": \"Question\", \"name\": \"Why does my second batch of grey trim look different?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"Most often the melt ran hot. At 200 \u00b0C instead of 188 \u00b0C the organic yellow pigment degrades, b* falls and \u0394E*ab rises from 0.6 to 2.6 against a limit of 1.0.\"}}, {\"@type\": \"Question\", \"name\": \"How is colour difference properly measured?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"As \u0394E*ab against a retained master using a spectrophotometer under D65 at 10\u00b0. Visual judgement under shop lighting is unreliable because metamerism can make two matching parts look different.\"}}, {\"@type\": \"Question\", \"name\": \"What \u0394E limit should I specify?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"1.0 or less for a visible architectural trim. Above 2.0 the difference is obvious on one elevation, which is why a 2.6 reading usually means replacing the whole installed run.\"}}, {\"@type\": \"Question\", \"name\": \"Does masterbatch dosing matter that much?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"Yes. 2.00 \u00b1 0.05% is the working tolerance. A 0.15% short dose shifts L* by about 1.5 units, which is already beyond most colour limits.\"}}, {\"@type\": \"Question\", \"name\": \"Can I use regrind on the visible face?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"No. Ten per cent regrind dilutes the pigment and lifts \u0394E by about 0.8 on its own, before any temperature drift is added. Keep regrind to the core or a hidden face.\"}}, {\"@type\": \"Question\", \"name\": \"What should the acceptance clause include?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"A retained master, the \u0394E limit under D65\/10\u00b0, dose tolerance, zone 3 temperature, and no regrind on the visible face. Both parties then measure the same numbers.\"}}]}<\/script><\/p>\n","protected":false},"excerpt":{"rendered":"<p>This guide ties the shift to melt temperature and masterbatch dose, and gives the four controls that settle a colour dispute before installation.<\/p>","protected":false},"author":1,"featured_media":9175,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-9177","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-plastic-extrusion-process"],"meta_box":{"post-to-quiz_to":[]},"_links":{"self":[{"href":"https:\/\/uplastech.com\/it\/wp-json\/wp\/v2\/posts\/9177","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/uplastech.com\/it\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/uplastech.com\/it\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/uplastech.com\/it\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/uplastech.com\/it\/wp-json\/wp\/v2\/comments?post=9177"}],"version-history":[{"count":1,"href":"https:\/\/uplastech.com\/it\/wp-json\/wp\/v2\/posts\/9177\/revisions"}],"predecessor-version":[{"id":9273,"href":"https:\/\/uplastech.com\/it\/wp-json\/wp\/v2\/posts\/9177\/revisions\/9273"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/uplastech.com\/it\/wp-json\/wp\/v2\/media\/9175"}],"wp:attachment":[{"href":"https:\/\/uplastech.com\/it\/wp-json\/wp\/v2\/media?parent=9177"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/uplastech.com\/it\/wp-json\/wp\/v2\/categories?post=9177"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/uplastech.com\/it\/wp-json\/wp\/v2\/tags?post=9177"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}